*SHOW ~ The families of British Non-marine Molluscs. 23 February 2007. 
 
*ITEM DESCRIPTIONS 
 
# \i{}Aciculidae\i0{}/
1,1 11,1 13<set on small protuberances>,2 20,1<the operculum excentric,
thin and horny> 21,2 22,5-5.5 23,2 25,2.2-2.5 26,1 27,2.2-2.5 28,0.8
30,2.5 31,2 32,0.6 33,2 36<almost>,1<gently tapered from the body whorl>
37,1<the suture appearing double, with the inner surface of the shell
showing through where is is attached to the preceding whorl> 38,1-2 39,1
40,1<almost straight-sided in section> 43,1<with widely spaced, sharply
incised transverse grooves> 44,5 45,3 47,1 48<very>,1<minute> 49,2<save
where the columellar edge of the mouth deflects over the umbilicus>
50,1<somewhat transparent> 51<light brown> 53,2<very glossy, striated
across the whorls> 55,1 56,2 59<in moist moss and leaf litter, mainly in
old deciduous woodland; tolerating non-calcareous soils> 61,2 66,1 67,1
68<\i{}Acicula\i0{} (1, Point snail)> 70<aciculid> 
 
# \i{}Acroloxidae\i0{}/
1,2<the latter represented by a small, rearwardly-directed apical point>
11,1 13,2 21<vestigially>,2/-<<@not ckeys>> 24,2 25,4-7 26,3 28,4-7<more
or less ovoid, and about half this across> 34,2<i.e., taking account of
the displaced vestige of the spire>/- 50,2 53,2 55,2 56,4<and gas
exchange also occurring via the skin in general> 59<in clean, still or
slow moving water, attaching to plants, submerged timber, or the shells
of larger molluscs> 61,1<but individuals acting as either male or female
when mating> 66,1 67,2 68<\i{}Acroloxus\i0{} (1, Lake limpet)>
70<acroloxi> 
 
# \i{}Agriolimacidae\i0{}/
1,4 2,15-50 3,2 5,2 6<very variable in colour and markings: buff, cream,
pale yellow, light to chestnut or dark brown, grey or black, often
flecked, sometimes rather translucent> 7,1/2 8,2 9,2 10,2 11,2<the
anterior pair short> 13,1 14,1<cf. \i{}Zonitidae\i0{}> 16,2 18,3
55,1/1-2<\i{}D. laeve\i0{}> 59<\i{}D. laeve\i0{} occurs in very wet
places - fens, river banks, water meadows, etc., where it can survive
submerged. The other species are found in gardens, parks, waste ground,
hedges, fields, meadows, pastures, etc., and \i{}D. reticulatum\i0{} is
a major agricultural and horticultural pest in lowland areas, where it
is perhaps the commonest British slug> 60<feeding mainly on living green
plants> 61,1 66,1 67,2 68<\i{}Deroceras\i0{} (4, Marsh, Field, and
Milky slugs)> 70<agriolim> 
 
# \i{}Ancylidae\i0{}/
1,2<the latter represented by the backward pointing apex> 11,1 13,2
21<vestigially>,2/-<<@not ckeys>> 24,1 25<width,>,4-8 26,3
28,4-8<somewhat less than this across, but much more broadly ovate than
those of \i{}Acroloxus lacustris\i0{}> 34,2<i.e., taking account of the
displaced vestige of the spire>/- 50,2 51<greyish horn-coloured, with
strong radiating striae and fine growth lines> 53,2 55,2 56,4<and gas
exchange also occurring via the skin in general> 59<\i{}A.
fluviatilis\i0{} lives in quick-flowing, soft or hard water, attached
firmly to stones and grazing on algae and mosses. \i{}F. wautieri\i0{},
by contrast, usually attaches to submerged plants in stagnant or slowly
moving water> 61,1<but individuals acting as either male or female when
mating> 66,1 67,2 68<Limpets: \i{}Ancylus\i0{}, \i{}Ferrissia\i0{}>
70<ancylida> 
 
# \i{}Arionidae\i0{}/
1,4 2,25-130 3,3<this sometimes represented by a few calcareous
granules> 5,1<this readily distinguishing Arionidae from the other slug
families> 6<variable in colour and often with much infra-specific
variation, as exemplified by the big, ubiquitous \i{}Arion ater\i0{},
which is often black but may be brick-red, orange or grey; but spotted
only in \i{}Geomalacus\i0{}> 7,1/2/3 8,2 9<shagreened, but>,3 11,2 13,1
16,1 18,2 55,1 59<species of diverse, moderately damp, usually sheltered
habitats> 61,1 66,1 67,2 68<\i{}Arion\i0{} (3, Large Black, Dusky,
Durham, etc., slugs), \i{}Geomalacus\i0{} (1, Kerry slug)>
70<arionida> 
 
# \i{}Assimineidae\i0{}/
1,1 20,1<the operculum horny, with spiral growth lines> 21,2 22,4-8<?>/-
23,2 25,1.7-2<\i{}Paludinella\i0{}>/4-6<\i{}Assiminea\i0{}> 26,1
27,1.7-2<\i{}Paludinella\i0{}>/4-6<\i{}Assiminea\i0{}>
28<about>,1.5-1.8<\i{}Paludinella\i0{}>/2.6-3.9<\i{}Assiminea\i0{}>
30,1.2<\i{}Paludinella\i0{}>/1.6<\i{}Assiminea\i0{}>
31,1<\i{}Paludinella\i0{}>/2<\i{}Assiminea\i0{}>
32,0.23<\i{}Paludinella\i0{}>/0.38<\i{}Assiminea\i0{}> 33,1<in \i{}A.
grayana\i0{}>/2<in \i{}Paludinella\i0{}> 36<shortly>,7<i.e., conical, in
\i{}A. grayana\i0{}>/5<in \i{}Paludinella\i0{}> 37,1<in \i{}A.
grayana\i0{}>/2<in \i{}Paludinella\i0{}> 40,1 45,3 47,2 49,1 50,2 53,2
55,1/3 56,2 59<coastal, found in shingle and plant dbris around the
high tide mark, sometimes submerged in brackish water, but more
terrestrial than aquatic> 61,2 66,1 67,1 68<\i{}Assiminea\i0{} (1, Dun
Sentinel), \i{}Paludinella\i0{} (1)> 70<assimine> 
 
# \i{}Bithyniidae\i0{}/
1,1 13,2 20,1<this thick, somewhat calcified, concentrically lined> 21,2
22,5/6 23,2 25,5-13(-16) 26,1 27,5-13(-16) 28<about>,3.25-8.5(-10.4)
30,1.5-1.55 31,1 32,0.3-0.35 33,1-2 36,5 37,2<very deeply so in \i{}B.
leachii\i0{}> 40,1 44,1-2 45,3 47,1-2 48,1<small> 49,1 50,1-2
51<horn-coloured> 53,2<glossy> 55,2 56,1 59<in large bodies of well
oxygenated, slow moving or still, hard water> 61,2 66,1 67,1
68<\i{}Bithynia\i0{} (2, Bithynia snails)> 70<bithynii> 
 
# \i{}Boettgerillidae\i0{}/
1,4 2,35-55 3,1 4,1 5,2 6<pale translucent greyish-yellow, the keel,
back and head darker bluish-grey, the sole pale yellow> 7,1 8,2
9<shagreened, and>,1 11,2<the anterior pair short> 13,1 16,2 18,1 55,1
58<somewhat>,1<the worm-like, extensible body adapting \i{}B.
palens\i0{} to life in shrinkage cracks, root holes and worm burrows>
59<associated with sub-surface crevices, in damp ground, in disturbed
places such as gardens, old quarries and roadside verges, especially
under lightly embedded stones or bricks> 61,1 66,1 67,2
68<\i{}Boettgerilla\i0{} (1, Worm slug)> 70<boettger> 
 
# \i{}Bradybaenidae\i0{}/
1,1 11,2 13,1 20,3 21,2 22,5-6.5 23,2 25,13-23 26,3 27,10-16 28,13-23
30,0.75 31,1 32,0.15 37,2 38,3 39,2 40,1 43,2<the growth ridges rather
coarse and irregular, and crossed by much finer spiral striations>
44,1-2 45,3 47,1 48<of medium width> 49,1<the lip everted basally, and
with a white internal rib> 50,2 51<white to pale greenish yellow>
53,2<though sometimes with a faint darker band at the periphery>
54<The animals sulphur-yellow to yellowish grey.> 55,1 59<found in Kent
in the shade, in lush, damp vegetation on roadside banks> 61,1 63,2
64,1<the reproductive structures including more than one dart sac> 65,1
66,1 67,2 68<\i{}Bradybaena\i0{} (1, Bush snail)> 69<This family is
probably indistinguishable from Helicidae on shell characters alone.>
70<bradybae> 
 
# \i{}Chondrinidae\i0{}/
1,1 11,2 13,1 20,3 21,2 22,8.5-10 23,2 25,6-8.5(-11) 26,1 27,6-8.5(-11)
28,2.3-2.8 30,2.76 31,2 32,0.64 33<fairly>,1 36,2/6 37<rather>,1 38,2
39,1-2 40,1 43,1<with very regular, fine ribbing> 45,1<usually with
about 9 teeth> 47,2<?> 49<fairly>,1<and deflected> 50,2 51<brown> 53,2
55,1 59<in dry, stony situations, mainly on chalk or limestone> 61,1
66,1 67,2 68<\i{}Abida\i0{} (1)> 70<chondrin> 
 
# \i{}Clausiliidae\i0{}/
1,1 11,2 13,1 20<mostly>,2<a flexible, spoon-shaped plate, attached to
the columella, which blocks the entrance when the animal
withdraws>/3<and lacking a clausilium, in \i{}Balea\i0{}> 21,2 22,9-13
23,1 25,8-17 26,1 27,8-17 28,2.2-4 30,3.7-4.3 31,2 32,0.64-0.7 36,2/6
37,1-2 38,1-2 39,1 40,1 43<usually more or less>,1<or finely
ribbed>/2<e.g., glossy and somewhat translucent in \i{}Cochlodina
laminata\i0{}> 44<relatively small,>,5 45,1<usually>/2<sometimes in
\i{}Balea\i0{}> 46,2 49<somewhat>,1 50,1/2 51<grey, yellowish- or
reddish-brown, blackish or horn-coloured, but commonly bleached grey>
53,1/1-2<sometimes streaked with white> 55,1 59<often in moss or ground
litter, or lichen-encrusted walls> 61,1 62,1<\i{}Balea\i0{}>/2 66,1 67,2
68<Door snails, Tree snails: \i{}Balea\i0{} (2), \i{}Clausilia\i0{}
(2), \i{}Cochlodina\i0{} (1), \i{}Macrogastra\i0{} (1)> 70<clausili> 
 
# \i{}Cochlicopidae\i0{}/
1,1 11,2 13,1 20,3 21,2
22,5.5<\i{}Cochlicopa\i0{}>/6.5-7<\i{}Azeca\i0{}> 23,2 25,4.5-7.5 26,1
27,4.5-7.5 28,2.1-3.2 30,2.3-2.5 31,2 32,0.46-0.54 33,2
36<shortly>,2-3/6 37<rather>,2/1 38,2 39,2 40<gently>,1<to almost
parallel> 44<obliquely>,5 45,1<\i{}Azeca\i0{}>/2 46,1-2 47,2 49,1<the
edge somewhat thickened and bluntly rounded, without a deflected lip>
50,1 51<yellowish horn-coloured, sometimes tinged with red or green>
53,2<smooth and glossy> 55,1 59<in mosses, herbage and ground litter in
diverse locations - woods, fields, hedge banks, marshes, sandhills,
etc.> 61,1 66,1 67,2 68<Moss snails: \i{}Azeca\i0{} (1),
\i{}Cochlicopa\i0{} (3)> 70<cochlico> 
 
# \i{}Discidae\i0{}/
1,1 11,2 12,1/2<\i{}Helicodiscus singleyanus\i0{} being subterranean and
blind> 13<when present,>,1 15,1 20,3 21,2
22,3.5-4<\i{}Helicodiscus\i0{}>/4-6<\i{}Discus\i0{}> 23,2
25,1.8-2.5<\i{}Helicodiscus\i0{}>/5.5-7<\i{}Discus\i0{}> 26,3
28,1.8-2.5<\i{}Helicodiscus\i0{}>/5.5-7<\i{}Discus\i0{}> 30,0.43-0.65
31,1-2 32,0.15-0.29 33,2 35,1/3 37,2 38,2-3 40,1/2 45,3 47,1 48,2
49,2<the mouth edge simple, not deflected> 50,1-2 51<yellowish- or
greenish-brown> 53,1<that of \i{}D. rotundatus\i0{} with regularly
spaced reddish-brown transverse stripes across the whorls>/2<in the
rest> 55,1 61,1 66,1 67,2 68<\i{}Discus\i0{} (2), \i{}Helicodiscus\i0{}
(1)> 70<discidae> 
 
# \i{}Dreissenidae\i0{}/
1,5 12,2<the animal with no head> 17,1 25,25-40 28,25-40<and about half
as long across> 29,1 50,2<and robust> 51<yellowish, brownish or greyish,
often with light-and-dark stripes> 55,2 56,3 59<in clean, well
oxygenated, lowland rivers, canals and reservoirs, attaching to stones
and other hard surfaces; sometimes in slightly brackish water> 66,2
68<\i{}Dreissena\i0{} (1, Zebra mussel)> 70<dreissen> 
 
# \i{}Ellobiidae\i0{}/
1,1 11,1 13,2<slightly behind them> 20,3 21,2
22,4.5-5<\i{}Carychium\i0{}>/5-7<\i{}Ovatella\i0{} and
\i{}Leucophytia\i0{}> 23,2
25,1.6-2.5<\i{}Carychium\i0{}>/5-8<\i{}Leucophytia\i0{},
\i{}Ovatella\i0{}> 26,1
27,1.6-2.5<\i{}Carychium\i0{}>/5-8<\i{}Leucophytia\i0{},
\i{}Ovatella\i0{}> 28,0.8-0.9<\i{}Carychium\i0{}>/2.5-3.8<approximately,
in \i{}Leucophytia\i0{} and \i{}Ovatella\i0{}> 30,1.8-2.1 31,2
32,0.3-0.47 33,1-2 36,6<in \i{}Ovatella\i0{} and
\i{}Leucophytia\i0{}>/3<\i{}Carychium\i0{}> 37,1-2<more deeply so in
\i{}Carychium\i0{}> 38,2 39,1-3 40,1 44,4<or auriculate> 45,1 46,2/3
47,2 49,1 50,1<\i{}Carychium\i0{}>/2<\i{}Ovatella\i0{} and
\i{}Leucophytia\i0{}> 51<colourless and semi-transparent when fresh in
\i{}Carychium\i0{}, and white, brown or yellowish in
\i{}Leucophytia\i0{} and \i{}Ovatella\i0{}> 53,2 55,1/1-2<\i{}Carychium
minimum\i0{} being more or less amphibious, common in moist places under
rotting logs or in leaf litter>/3<\i{}Ovatella\i0{} and
\i{}Leucophytia\i0{}, living around high tide mark, but terrestrial
rather than aquatic> 56,2 61,1<but individuals acting as either male or
female when mating> 66,1 67,2 68<\i{}Carychium\i0{} (2, Herald snails,
Sedge snail), \i{}Leucophytia\i0{} (1), \i{}Ovatella\i0{} (1,
Mouse-eared snail)> 70<ellobiid> 
 
# \i{}Enidae\i0{}/
1,1 11,2 13,1 20,3 21,2 22,6.5-8 23,2 25,8.5-9 26,1 27,8.5-9<\i{}E.
obscura\i0{}>/14-17<\i{}E. montana\i0{}> 28,3.7<\i{}E.
oscura\i0{}>/6.7<\i{}E. montana\i0{}> 30,2.32-2.33 31,2 32,0.49-0.52
33,1-2 36,6 37<fairly>,1 38,2 39,1-2 40,1 43,2<sculptured only with fine
growth lines and/or striae> 45,3 46,2 47,1 48,1<and deep> 49,1 50,1-2
51<light brown or transparent horn-coloured, not very glossy> 53,2 55,1
59<in ground litter in woods, hedgerows, etc., mainly on base-rich
soils, often climbing up tree trunks or walls in wet weather> 61,1 66,1
67,2 68<\i{}Ena\i0{} (2, Bulin snails)> 70<enidae> 
 
# \i{}Euconulidae\i0{}/
1,1 11,2 13,1 20,3 21,2 22,5.5 23,2 25,2.3-3.5 26,3
27<about>,2.3-2.8<\i{}E. fulvus\i0{}>/1.6-2<\i{}E. alderi\i0{}>
28,2.8-3.5<\i{}E. fulvus\i0{}>/2.3-2.8<\i{}E. alderi\i0{}> 30,0.72-0.8
31,2 32,0.31-0.36 33,2 35,3 37,2 38,2 39,2 40,1 44,4 45,3 47,1-2 48<if
not closed,>,1<minute> 49,2<the mouth edge simple> 50,1 51<horn-coloured
or pale yellowish brown, glossy or silky-glossy, but appearing almost
black in life in the dark-bodied \i{}E. alderi\i0{}> 53,2 54<The body of
the animal pale in \i{}E. fulvus\i0{}, dark in \i{}E. alderi\i0{}.> 55,1
59<in a wide variety of moist, sheltered, undisturbed habitats - in
coniferous and deciduous woods, mossy hedge banks, dune slacks and
marshes> 61,1 66,1 67,2 68<\i{}Euconulus\i0{} (2, Glass snails)>
70<euconul> 
 
# \i{}Ferussaciidae\i0{}/
1,1 11,2 12,2<\i{}C. acicula\i0{} being subterranean and blind> 20,3
21,2 22,5.5 23,2 25,4.5-5.5 26,1 27,4.5-5.5 28,1.2 30,3.19 31,2 32,0.45
33,2 36,6 37,1 38,1-2 39,1 40,1 45,3 46,2-3 47,2 49,2<the mouth edge
simple and delicate> 50,1<in life, becoming opaque after the death of
the animal> 51<pale or white, and very glossy> 53,2 54<The body of the
animal colourless.> 55,1 58,1<in unwooded calcareous habitats, sometimes
occurring at depths of 2 metres or more, often in rock crevices, rootlet
holes, or in the cavities within old bones> 61,1 66,1 67,2
68<\i{}Cecilioides\i0{} (1, Blind snail, Agate snail)> 70<ferussac> 
 
# \i{}Helicidae\i0{}/
1,1 11,2 13,1 20,3 21,1<\i{}Helicodonta\i0{}>/2<the rest, but some
discoid, with the spire scarcely raised> 22,(4-)5-7<mostly>/8-10 23,2
25,(5-)6-40(-50)<wide>/10-25(-40)<high> 26,1<conspicuously so only in
\i{}Cochlicella\i0{}>/2<more or less,in \i{}Trochoidea elegans\i0{},
\i{}Helix aspersa\i0{}, \i{}H. pomatia\i0{} and \i{}Arianta
arbustorum\i0{}>/3<mostly, at least somewhat> 27,3.5-50 28,5-50<the
measurements and proportions reflecting great variation in sizes and
shapes among, and sometimes within, the genera>
30,0.45<\i{}Helicodonta\i0{}>/0.59-1<mostly>/1.8-2<\i{}Cochlicella\i0{}>
31,1/2
32,0.09-0.32<mostly>/0.57-0.66<\i{}Cochlicella\i0{}>/-<inapplicable to
the planispiral in \i{}Helicodonta\i0{}> 33,1<in
\i{}Cochlicella\i0{}>/2<mostly> 35<when not or scarcely higher than
wide,>,1<in \i{}Helicella\i0{}, and more or less so in \i{}Helicogona
lapicida\i0{}>/2<in \i{}Trochoidea elegans\i0{} and \i{}Cochlicalla
barbara\i0{}>/3<most commonly>/4-5<in \i{}Helix aspersa\i0{} and \i{}H.
pomatia\i0{}> 36<when markedly higher than wide, i.e. in
\i{}Cochlicella\i0{},>,6/7 37,1/2/1-2 40,1<mostly>/2<\i{}Perforatella
subrufescens\i0{}>/3<\i{}Trochoidea\i0{}, \i{}Hygromia\i0{},
\i{}Helicogona\i0{}> 42,1/2 45,3 47,1 49,1 50,2 51<variously white,
yellow, pink, horn-coloured, or brown> 53,1<often strikingly banded
along or occasionally across the whorls>/2 55,1 59<mostly in dry, sunny,
open, especially calcareous places, in quarries, stone walls, hedgerows,
waste ground, gardens, etc.; but a few confined to moist and sheltered
or marshy places, or woodland> 61,1 63,1 64,1 65,1<the darts exhibit
characteristic shapes and sculpting, for example providing ready means
of distinguishing \i{}C. hortensis\i0{} from \i{}C. nemoralis\i0{} - see
illustrations> 66,1 67,2 68<\i{}Arianta\i0{} (1, Copse snail),
\i{}Ashfordia\i0{} (1, Silky snail), \i{}Candidula\i0{} (2, Wrinkled
snail), \i{}Cepaea\i0{} (2, Grove snail and White-lipped snail),
\i{}Cernuella\i0{} (1, Striped snail, Zoned snail),
\i{}Cochlicella\i0{} (2, Pointed snails), \i{}Helicodonta\i0{} (1,
Cheese snail), \i{}Helicella\i0{} (1, Heath snail),
\i{}Helicogona\i0{} (1, Lapidary snail), \i{}Helix\i0{} (including
\i{}Cantareus\i0{}) (2, Garden snail, and Edible or Roman snail),
\i{}Hygromia\i0{} (2, Girdled snail and Hedge snail), \i{}Monacha\i0{}
(2, Carthusian snail and Kentish snail), \i{}Perforatella\i0{} (2,
Brown snail), \i{}Ponentina\i0{} (1), \i{}Trichia\i0{} (3, including
Strawberry snail and Hairy snail), \i{}Theba\i0{} (1, White snail,
Sandhill snail), \i{}Trochoidea\i0{} (2, Top snails)> 70<helicida> 
 
# \i{}Hydrobiidae\i0{}/
1,1 20,1<this thin, horny, spirally lined> 21,2 22,4/5-6/7-8 23,2
25,2.5-6(-9) 26,1 27,2.5-6(-9) 30,1.7-2.3 31,2 32,0.4-0.5 33,1-2
36,5/6/7 37,2<between all the whorls> 40,1 44,2 45,3 47,1 48,1<small>
49,1 50,1-2 51<horn-coloured> 53,2 55,2/3 56,1 59<variously in still,
slow or fast moving, fresh or brackish water> 61,2 66,1 67,1
68<\i{}Hydrobia\i0{} (3, Spire snails), \i{}Heleobia\i0{} (1),
\i{}Mercuria\i0{} (1, Swollen Spire snail), \i{}Marstoniopsis\i0{} (1,
Taylors Spire snail), \i{}Potamopyrgus\i0{} (1, Jenkins's Spire
snail)> 70<hydrobii> 
 
# \i{}Limacidae\i0{}/
1,4 2,35-200 3,2 5,2 6<variable in colour: cream, ashy-black to grey or
greenish-grey, yellow or pale brown, sometimes mottled or longitudinally
dark-banded or striped> 7,1/2/4<e.g., in \i{}Limax flavus\i0{} and
\i{}L. tenellus\i0{}> 8,2 9,2 10,1 11,2<the anterior pair short> 13,1
14,1<cf. \i{}Zonitidae\i0{}> 16,2 18,3 55,1 59<mainly naturally woodland
ground dwellers or climbers, or especially in places associated with
human activities (gardens, rubbish tips, roadsides, ploughed fields,
etc.), in moist ground litter and herbage; nocturnal, hiding by day
under logs, stones, bark, etc.> 60<seemingly feeding mostly on algae,
fungi and deacaying vegetable mater, rather than on living plants> 61,1
66,1 67,2 68<\i{}Lehmannia\i0{} (2, Tree slug, Greenhouse slug),
\i{}Limax\i0{} (4, Great Grey, Ash-black, and Yellow slugs),
\i{}Malacolimax\i0{} (1, Slender slug)> 70<limacida> 
 
# \i{}Lymnaeidae\i0{}/
1,1 11,1<these broad-based, triangular, and flattened> 13,2 20,3 21,2
22,3-8 23,2/1<<@not ckeys> exemplified in particular by aberrant
populations of \i{}Lymnaea peregra\i0{}> 25,(7-)10-45(-50)
26,1<mostly>/1-2 27,(7-)10-45(-50) 30,1.2-2.8 32,0.05-0.48 33,1<even
when very short> 34,2<notably in \i{}Lymnaea auricularia\i0{}, \i{}Myxas
glutinosa\i0{} and forms of \i{}L. peregra\i0{}>/1<mostly> 35<when wider
than high,>,6 36<when higher than wide,>,2<broadly>/4/5/6/7
37,2<especially so at the base of the spire> 40,1 45,3 46,2/3 49,1<the
aperture often strengthened by a thickened rib>/2 50,1-2 51<mostly more
or less horn-coloured, sometimes brown-, purplish- or greyish-tinged,
but sometimes rendered blackish by extraneous matter> 53,2 55,1-2/2
56,2<and via the skin in general> 59<species of diverse wet and aquatic
habitats, often on emergent vegetation or tolerant of seasonal
dessication. \i{}L. truncatula\i0{}, living in wet places but mostly out
of water, is notorious as the intermediate host of \i{}Fasciola
hepatica\i0{}, the sheep liver fluke> 61,1<but individuals acting as
either male or female when mating> 66,1 67,2 68<\i{}Lymnaea\i0{} (6,
Pond snails), \i{}Myxas\i0{} (1)> 70<lymnaeid> 
 
# \i{}Margaritiferidae\i0{}/
1,5 12,2<the animal with no head> 17,2 25<breadth>,90-170 28,90-170<and
about half as long across the shell from the hinge> 29,2 50,2<and
robust> 51<dull black, the interior pearly white or pinkish> 52,1 55,2
56,3 59<restricted to clean, cool, fast-flowing rivers and streams at
higher elevations, on sandy, gravelly or pebbly substrates; burrowing
into interstices in the substrate> 66,2 68<\i{}Margaritifera\i0{} (1,
Freshwater or Scottish Pearl Mussel)> 70<margarit> 
 
# \i{}Milacidae\i0{}/
1,4 2,45-75 3,1 5,2 6<variable in colour: black, brown or dark-,
brownish- or yellowish-grey, sometimes speckled or reticulated with
black> 7,1/2 8,2 9<shagreened, and>,1 11,2<the anterior pair short> 13,1
14,2<?> 16,2 18,1 55,1 58<rather>,1<\i{}T. sowerbyi\i0{}>/2 59<in woods
and hedges, gardens and fields, \i{}M. gagates\i0{}, \i{}T.
budapestensis\i0{} and \i{}T. sowerbyi\i0{} being notable pests>
60<herbivorous> 61,1 66,1 67,2 68<\i{}Milax\i0{} (1, Jet slug),
\i{}Tandonia\i0{} (3, Keeled slug, Budapest slug)> 70<milacida> 
 
# \i{}Neritidae\i0{}/
1,1 20,1<the operculum calcareous and solid, with an apophysis> 21,2
22,3 23,2 25,(8.25-)9-13 26,3 27<about>,(7.3-)8-11.6 28,(8.25-)9-13
30,0.9 31,1 32,0.15 34<semi-lunate,>,2 35,6 37,2<at the junction of the
body whorl and the spire> 40,2 45,3 47,2 49,1 50,2 51<basically whitish
or yellow to brown or even black> 53,1<with irregular purple, pink or
white variegations, or transverse bands, or spirally marked with three
dark bands> 55,2 56,1 59<restricted to well oxygenated waters, in
rivers, canals and lakes> 61,2 66,1 67,1 68<\i{}Theodoxus\i0{} (1,
River Nerite)> 70<neritida> 
 
# \i{}Physidae\i0{}/
1,1 11,1 13,2 20,3 21,2 22,4-7 23,1 25,8-18 26,1 27,8-12<\i{}P.
fontinalis\i0{}>/10-18<introduced species>
30,1.5-1.7<\i{}Physa\i0{}>/2.7<\i{}Aplexa\i0{}> 31,1<in
\i{}Physa\i0{}>/2<in \i{}Aplexa\i0{}>
32,0.1-0.2<\i{}Physa\i0{}>/2.7<\i{}Aplexa\i0{}> 36,2<in
\i{}Aplexa\i0{}>/5<the \i{}Physa\i0{} spp. being much less elongate>
40,1 45,3 49,1-2 50,1<glossy> 51<yellowish- or reddish-horn coloured or
even red in \i{}Aplexa\i0{}, pale horn-coloured to dark brown or
blackish in \i{}Physa\i0{}> 53,2 54<The animals grey to almost black.>
55,2 56,2<and via the skin in general> 59<the native \i{}Physa
fontinalis\i0{} occurs on aquatic plants in still or running, hard or
soft, unpolluted water, while the introduced \i{}Physa\i0{} species are
more tolerant of de-oxygenated conditions and pollution. \i{}Aplexa
hypnorum\i0{}, which can survive periodic dessiccation, is found on
vegetation in swampy pools, roadside ditches and small, grassy ponds>
61,1<but individuals acting as either male or female when mating> 66,1
67,2 68<\i{}Aplexa\i0{} (1), \i{}Physa\i0{} (1 native, plus 2 or 3
introduced: Bladder snails)> 70<physidae> 
 
# \i{}Planorbidae\i0{}/
1,1 11,1 13,2 20,3 21,1<nearly always>/2<in \i{}Gyraulus crista\i0{}
only> 22,3-8 23,1<when correctly interpreted, although carried by the
animal upside down and hence appearing dextral when illustrated in its
natural position. The morphologically upper side, as determined by the
anatomy, is that which is uppermost when the shell is held with its
aperture to the left of the observer> 25,2-17/25-35<\i{}Planorbarius
corneus\i0{}> 26,3 28,2-17/25-35<\i{}Planorbarius corneus\i0{}>
30,(0.15-)0.2-0.36(-0.44) 32,0.12<in the discoid \i{}Gyraulus
crista\i0{}, the rest being planispiral>/- 33,2 35<in \i{}Gyraulus
crista\i0{}, where the spire is raised,>,1/- 40,1/2/3 42,1<notably in
\i{}Gyraulus crista\i0{}, and in the Nautilus-like, internally segmented
\i{}Segmentina nitida\i0{}>/2<then sometimes conspicuously ridged at
irregular intervals> 45,3 47,1 48,2 49,1-2 50,1-2 51<yellowish, brownish
or olivaceous horn-coloured, occasionally whitish, sometimes more or
less translucent, but often darkened by extraneous matter so as to
appear blackish> 53,2 54<Unlike that of most molluscs, the blood
contains haemoglobin, so that a popular aquarium form of \i{}P.
corneus\i0{} with a translucent shell and lacking body pigment is bright
red.> 55,2 56,2<and via the skin in general> 59<water snails of diverse,
well-vegetated aquatic habitats, with some species tolerant of seasonal
dessication> 61,1<but individuals acting as either male or female when
mating> 66,1 67,2 68<Rams-horn snails: \i{}Anisus\i0{} (3),
\i{}Bathyomphalus\i0{} (1), \i{}Gyraulus\i0{} (4), \i{}Hippeutis\i0{}
(1), \i{}Menetus\i0{} (1), \i{}Planorbarius\i0{} (1), \i{}Planorbis\i0{}
(2), \i{}Segmentina\i0{} (1)> 70<planorbi> 
 
# \i{}Pomatiasidae\i0{}/
1,1 11,1 13,2 20,1<this thick, testaceous, somewhat calcified> 21,2
22,4.5-5 23,2 25,12-16 26,1 27,12-16 28,9-11.5 30,1.4 31,1-2 32,0.3 36,5
37,2<between all the whorls> 38,1 39,1 40,1 44,1 45,3 47,1 48,1<small,
but deep> 49,1 50,2<thick and solid, with a reticulate sculpture of fine
spiral and transverse ribs, the former more pronounced at least near the
base of the shell> 51<light pinkish or greyish violet to yellowish, with
darker streaks or spots> 53<fairly>,1-2 55,1 56,2 59<strictly calcicole,
burrowing into in loose rubble in hedge banks, quarries, open woods,
cliffs, and maritime grassland> 61,2<the shells of females often
slightly larger> 66,1 67,1 68<\i{}Pomatias\i0{} (1, Round-mouthed
snail)> 70<pomatias> 
 
# \i{}Punctidae\i0{}/
1,1 11,2 13,1 15,2 20,3 21,2 22,3.5-4 23,2 25,1.2-2 26,3
27<about>,0.7-0.85<\i{}Punctum pygmaeum\i0{}>/1.2-1.3<\i{}Paralaoma
caputspinulae\i0{}> 28,1.2-1.5<\i{}P. pygmaeum\i0{}>/1.8-2<\i{}Paralaoma
caputspinulae\i0{}> 30,0.62-0.7 31,1 32,0.15-0.21 33,2 35,3 37,2 38,2
39,2 40,1 42,2<but with numerous very fine, regular growth ridges,
lending a sheen> 45,3 47,1 48,2<shallow> 49,2<the mouth edge thin and
brittle, not deflected> 50,2 51<golden brown in \i{}Punctum\i0{}> 53,2
55,1 59<in leaf litter, etc., in moist places> 61,1 66,1 67,2
68<\i{}Paralaoma\i0{} (1), \i{}Punctum\i0{} (1, Dwarf snail)>
70<punctiid> 
 
# \i{}Pupillidae\i0{}/
1,1 11,2<with a short anterior pair, by contrast with the
\i{}Vertiginidae\i0{}> 13,1 20,3 21,2 22,6-7 23,2 25,3-4.4 26,1 27,3-4.4
28,1.7-1.9 30,1.74-2.1 32,0.48-0.62 33,2 36,3 37<rather>,1-2 38,2 39,1-2
40,1 43,1-2<with only feeble growth lines> 45,1<sometimes conspicuous,
as in \i{}Leiostyla\i0{}, often much reduced, but usually with at least
an angular>/2/3<rarely> 46,2 47,1 49,1-2<the mouth edge often deflected>
50,1-2 51<brown or horn-coloured, glossy or dull> 53,2 55,1 59<in
diverse locations, moist or dry> 61,1 62,1<\i{}Lauria\i0{}>/2 66,1 67,2
68<"Chrysalis snails": \i{}Lauria\i0{} (2), \i{}Leiostyla\i0{} (1),
\i{}Pupilla\i0{} (1)> 70<pupillid> 
 
# \i{}Pyramidulidae\i0{}/
1,1 11,2 13,1 20,3 21,2 22,4.5 23,2 25,2.5-3 26,3 27,1.5-2 28,2.5-3
30,0.56 31,2 32,0.39 33,2 35,3 37,2 38,3 39,2-3 40<bluntly>,2/-
44<gibbous> 45,3 47,1 48,2<and deep> 49,2<the edge brittle> 50,2<the
well defined growth ridges bestowing a silky aspect> 51<dark
horn-coloured or reddish brown, weathering to almost white> 53,2 55,1
59<grazing nocturnally or in wet weather on lichens and algae on
limestone rocks and walls, or associated with calcareous mortar, in
locations exposed to the sun> 61,1 62,1 66,1 67,2 68<\i{}Pyramidula\i0{}
(1, Rock snail)> 70<pyramidu> 
 
# \i{}Sphaeriidae\i0{}/
1,5 12,2<the animals with no developed head> 17,2
25,1.5-11<\i{}Pisidium\i0{}>/7-22 28,1.5-11<\i{}Pisidium\i0{}>/7-22<and
usually about two thirds as long from the hinge to the front> 29,3
50,1/2<but thin relative to that of other British mussels> 51<greyish-,
creamy-, yellowish or greenish horn-coloured, glossy> 55,2 56,3 59<in
diverse aquatic habitats, some species tolerating seasonal drying up>
66,2 68<Orb mussels, Pea Shells: \i{}Musculium\i0{} (2),
\i{}Pisidium\i0{} (17), \i{}Sphaerium\i0{} (3)> 70<sphaerii> 
 
# \i{}Succineidae\i0{}/
1,1 11,2<but the anterior pair is vestigial>/- 13,1 20,3 21,2 22,3 23,2
25,5-17(-22) 26,1 27,5-17(-22) 28<approximately>,4.25-7 30,1.6-1.9
31,1-2 32,0.1-0.23 33,1-2 36<somewhat>,4/5<"succiniform"> 37,2 38,2-3
39,2-3 40,1 44,1-3 45,3 46,1 47,2 49,2 50,1<glossy> 51<amber-coloured or
greenish> 53,2 55,1 59<in a diversity of damp, natural habitats> 61,1
66,1 67,2 68<Amber snails: \i{}Catinella\i0{} (1), \i{}Oxyloma\i0{}
(2), \i{}Succinea\i0{} (1)> 70<succinei> 
 
# \i{}Testacellidae\i0{}/
1,3 2,60-100 5,2 6<creamy white or yellow, or brown, sometimes speckled
above with black or brown> 8,1 9,- 11,2<the anterior pair short> 13,1
55,1 57,1 58,1<living in burrows several cm deep, and emerging at night
to feed mainly on earthworms, but sometimes on other small animals. The
seized earthworm withdraws into its burrow, where it is consumed at
leisure by the \i{}Testacella\i0{} which is dragged down with it. Hard
to find, but best sought in well-manured, worm-rich ground> 61,1 66,1
67,2 68<\i{}Testacella\i0{} (3, Shelled slug, Shield slug, Maugs
slug)> 69<Muscular animals, broad behind and tapering to the small
head, which bears two pairs of short, slender tentacles that are not
swollen at their tips; with a very large radula, no jaw, and the anus at
the hind end.> 70<testacel> 
 
# \i{}Truncatellidae\i0{}/
1,1 11,1 13,2 20,1 21,2 22,3/4 23,2 25,3.5-5 26,1 27,3.5-5
28<approximately>,1.5-1.75 30,2.5 31,2 32,0.5 33,3 36,1 37,2<between all
the whorls> 38,2 39,2 40,1 45,3 49,2 50,1 51<transmitting the pinkish
colour of the animal> 53,2 55,3 59<living around the high tide level, in
driftwood, etc., and in salt-marshes> 66,1 67,1 68<\i{}Truncatella\i0{}
(1, Looping snail)> 70<truncate> 
 
# \i{}Unionidae\i0{}/
1,5 12,2<the animals with no developed head> 17,2 25,(55-)70-130(-200)
28,(55-)70-130(-200)<about half as long across the shell from the hinge,
somewhat more in \i{}A. anatina\i0{}> 29,2/3 50,2<and robust> 51<brown,
bright or dark greenish or greenish brown, glossy> 52,2 55,2 56,3
59<burrowing in the substrate, in still or slow-moving waters - rivers,
canals, lakes and reservoirs> 66,2 68<\i{}Anodonta\i0{} (2, Swan mussel
and Duck mussel), \i{}Pseudanodonta\i0{} (1, Compressed River
mussel), \i{}Unio\i0{} (2, including Painters mussel and Swollen
River mussel)> 70<unionida> 
 
# \i{}Valloniidae\i0{}/
1,1 11,2 13,1 20,3 21,2<but only slightly raised in \i{}Vallonia\i0{}>
22,3-3.25<\i{}Vallonia\i0{}>/4<\i{}Acanthinula\i0{}>/5.5-6<\i{}Spermodea\i0{}>
23,2 25,2-2.7
26,2<\i{}Acanthinula\i0{}>/2-3<\i{}Spermodea\i0{}>/3<\i{}Vallonia\i0{}>
27,2<\i{}Acanthinula\i0{}>/2-2.7<\i{}Spermodea\i0{}, \i{}Vallonia\i0{}>
28,2<\i{}Acanthinula\i0{},
\i{}Spermodea\i0{}>/1.25-1.4<\i{}Vallonia\i0{}>
30,0.5-0.55<\i{}Vallonia\i0{}>/0.81<\i{}Spermodea\i0{}>/1.13<\i{}Acanthinula\i0{}>
31,1<in \i{}Vallonia\i0{}>/2
32,0.14-1.18<\i{}Vallonia\i0{}>/0.33<\i{}Acanthinula\i0{} and
\i{}Spermodea\i0{}> 33<when raised,>,2 35<when wider than high,>,1/3<in
\i{}Vallonia\i0{}>/3-5<in \i{}Spermodea\i0{}> 36<when higher than wide,
broadly>,5<in \i{}Acanthinula\i0{}> 38,3 40,1-2/3<in
\i{}Acanthinula\i0{}> 41,1<in \i{}Acanthinula\i0{} only, the spines
derived via prolongations from the transverse ridges, along the keel>/2
42,1<\i{}V. costata\i0{}, \i{}Spermodea lamellata\i0{}, and
\i{}Acanthinula\i0{}>/2 44,1 45,3 47,1 48,2<open> 49,1<the mouth edge
more or less expanded to form a flat lip> 50,1/2 51<greyish white or
translucent (\i{}Vallonia\i0{}), pale golden brown (\i{}Spermodea\i0{}),
or brown (unweathered \i{}Acanthinula\i0{})> 53,2 55,1 59<in diverse
habitats> 61,1 64,1<the \i{}Vallonia\i0{} species being equipped with a
dart sac secreting a straight, simple dart: cf. Ellis>/2 66,1 67,2
68<\i{}Acanthinula\i0{} (1, Prickly snail), \i{}Spermodea\i0{} (1,
Plated snail), \i{}Vallonia\i0{} (3, Grass snails)> 70<vallonii> 
 
# \i{}Valvatidae\i0{}/
1,1 13<sub->,2 20,1<this circular, horny and thin, concentrically
multi-spiral> 21,1<\i{}V. cristata\i0{}>/2 22,5/6 23,2 25,3-6
26,3/2<\i{}V. piscinalis\i0{}> 27,1.2-1.6<\i{}V.
cristata\i0{}>/3-4.3<\i{}V. macrostoma\i0{}>/4.5-6<about, in the high
spired \i{}V. piscinalis\i0{}> 28,3-3.5(-4)<\i{}V.
cristata\i0{}>/3.5-5<\i{}V. macrostoma\i0{}>/4.5-6<about, in \i{}V.
piscinalis\i0{}> 30,0.6<\i{}V. macrostoma\i0{}>/1<\i{}V.
piscinalis\i0{}> 32,0.17<\i{}V. macrostoma\i0{}>/0.24<\i{}V.
piscinalis\i0{}> 33<when raised,>,2 35<when not planispiral,>,1<\i{}V.
macrostoma\i0{}>/3-5<\i{}V. piscinalis\i0{}> 37<when raised,>,2 40,1
44,1 45,3 46,1 47,1/2<\i{}V. piscinalis\i0{}> 48<when present,>,2<and
deep> 49,1-2 50,2 51<brownish-yellow or horn-coloured> 53,2 55,2
56,1<the left gill feather-like and exsertile, the right thread-like>
59<in slowly flowing or still water, often on muddy or silty substrates>
61,1 66,1 67,1 68<\i{}Valvata\i0{} (3, Valve snails)> 70<valvatid> 
 
# \i{}Vertiginidae\i0{}/
1,1 11,1 13,1<i.e., on the only pair> 20,3 21,2 22,4.5-6.5 23,1<some
\i{}Vertigo\i0{} spp.>/2 25,1.7-3.5(-4) 26,1 27,1.7-3.5(-4) 28,0.9-1.5
30,1.5-2.05 31,2 32,0.38-0.58 33,2 36,1/3 37,2 38,1-3 39,1-3 40,1 43,1-2
45,1<\i{}Vertigo\i0{}>/2<\i{}Columella\i0{}, \i{}Truncatellina\i0{}>
46,2 47,1<small>/2 48<when present,>,1 49,2<though the the mouth edge is
sometimes slightly expanded> 50,1/1-2 51<pale to dark brown or
horn-coloured, dull or glossy> 53,2 55,1 59<in a diversity of wet or dry
habitats> 61,1 66,1 67,2 68<Chrysalis snails, Whorl snails:
\i{}Columella\i0{} (3), \i{}Truncatellina\i0{} (2), \i{}Vertigo\i0{}
(11)> 70<vertigin> 
 
# \i{}Vitrinidae\i0{}/
1,1 11,2<but the anterior pair small and inconspicuous> 13,1 19,1 20,3
21,2 22,1.75-4 23,2 25,4.5-6 26,3 28,4.5-6 30,0.48-0.64 31,1<the spire
scarcely raised> 32,0.04-0.15 33,2 35,3/6<auriculate in
\i{}Semilimax\i0{}> 37,1-2 40,1 45,3 47,2 48,1 49,2<the edge of the
mouth thin and delicate, often with a non-calcified strip along its
lower edge> 50,1 51<transparent, greenish, glossy> 53,2 55,1 59<\i{}V.
pellucida\i0{} ecologicaly catholic, in moist or dry coniferous and
deciduous woods, quarries, stabilized dunes, etc., the others in and
under moist leaf litter and fallen branches in woodland> 61,1 64,1 65,2
66,1 67,2 68<Glass snails: \i{}Phenacolimax\i0{} (1),
\i{}Semilimax\i0{} (1), \i{}Vitrina\i0{} (1)> 70<vitrinid> 
 
# \i{}Viviparidae\i0{}/
1,1 20,1<this horny and thin or fairly thick, concentrically lined> 21,2
22,6-7 23,2 25,25-35<\i{}V. viviparus\i0{}>/30-40<\i{}V. contectus\i0{}>
26,1 27,25-35<\i{}V. viviparus\i0{}>/30-40<\i{}V. contectus\i0{}>
28<about>,18-26<\i{}V. viviparus\i0{}>/23.5-31.8<\i{}V. contectus\i0{}>
30,1.2-1.3 32,0.22-0.25 36,5 37,2<between all the whorls> 40,1
44<almost>,1 45,3 47,1/2 48,1<deep and distinct, in V.
\i{}contectus\i0{} only> 49,1 50,2 51<dark greenish with darker bands>
53,1 55,2 56,1 59<in large bodies of well oxygenated, still or
slow-moving water> 60<suspension feeders, lying for long periods in mud
with the mouth uppermost> 61,2 62,1 66,1 67,1 68<Viviparus (2, River
snails)> 70<vivipari> 
 
# \i{}Zonitidae\i0{}/
1,1 11,2 13,1 14,1<cf. \i{}Limacidae\i0{}, etc.> 20,3 21,2<but often
only slightly raised> 22,3.5-6(-7) 23,2 25,2.2-15 26,3 28,2.2-15
30,0.43-0.59 31,1 32,0.1-0.18/0.2-0.28<\i{}Zonitoides\i0{}> 33,2 35<more
or less>,1/3 37,2 38,2-3 39,1-2 40,1 45,3 47,1-2 48,1-2<variable in
depth, with, and symmetry> 49,2<the mouth edge delicate, not deflected>
50<in life, mostly>,1<and usually glossy, but often becoming opaque
after death of the animal> 51<often clear horn-coloured, fawn, brownish
or whitish> 53,2 54<The body of the animal is often tinted bluish.> 55,1
59<in vegetation and ground litter, under logs and stones, etc., in
diverse habitats> 61,1 64,1<the \i{}Zonitoides\i0{} species>/2 65,1 66,1
67,2 68<Glass snails and Garlic snails: \i{}Aegopinella\i0{} (2),
\i{}Nesovitrea\i0{} (2), \i{}Oxychilus\i0{} (4), \i{}Vitrea\i0{} (3),
\i{}Zonitoides\i0{} (2)> 70<zonitida> 
