Throughout this key the following abbreviations are used for A Key to the British habitat types in which the molluscs occur:

FRESH AND BRACKISH WATER RH River - hard water RS - River soft water GASTROPODS R - River hard or soft S - Stream L - Lake FRESHWATER BIOLOGICAL ASSOCIATION P - Pond SCIENTIFIC PUBLICATION No. 13 C - Canal Edition 4 1977 G - Grazing level drain T - Temporary water by U – Ubiquitous T.T.Macan B - Brackish

And below for the status as of March 2007 Illustrated by Douglas Cooper W Widespread L Local Now out of print. R rare or Modified with name changes, R1 R2 R3 for Red Data Book species 1, 2 or 3 additional data on habitats and species status. One species, Physa heterostropha , This extra data is presented thus: deleted from the British list (hab: RH, S )(stat: R2 ) and one, Ferrissia clessiniana, added

A. Chalkley Spring 2007 & Autumn 2008

Version 5, May 2009 Page 1 of 15

1 Snails with an 2

..... Snails without an operculum 15 2 Shell globose, with a very low spire; robust, resembling a marine rather than a freshwater species; half-moon shaped; operculum calcified, with an internal rib; shell with variable markings, usually a pattern of purple, pink or white variegations on a yellow, brown, or black background; (gill feather-like, i.e. with laminae on both sides of the axis) (hab: RH, S )(stat: W )

Theodoxus fluviatilis (Linn.) The Nerite ..... Shell of other shape; aperture more or less round; pattern, if present, 3 not variegated 3 Shell over 30 mm high; usually banded; (operculum with concentric 4 rings; gill comb-like, not protrusible)

..... Shell less than 15 mm high; seldom banded 5 4 Shell glossy; rather large and conspicuous; whorls rather tumid and high-shouldered; suture deep; pointed (hab: RH, C ) (stat: L ) Viviparus contectus (Mull.) Lister’s River Snail

..... Shell not glossy; umbilicus scarcely apparent; whorls neither tumid nor high-shouldered; suture shallow; apex without a conspicuous point (hab: RH, C )(stat: W ) Viviparus viviparus (Linn.) The River Snail 5(3) Shell, if higher than broad, only just so; gills protrusible, left gill 6 feather-like, right gill thread-like; (operculum with a spiral line)

..... Shell distinctly higher than broad; gill not protrusible, and comb-like, 8 i.e. with laminae on one side only of the axis 6 Shell flat and disc-like, resembling a small ; (shell glossy; curvature of whorls slightly flattened above and a, Theodoxus fluviatilis b, Viviparus contectus below) c, Viviparus viviparous d, Valvata cristata (hab: R, L , S, P, C, G )(stat: W ) Valvata cristata (Mull.) Flat Valve Snail

..... Shell not flat and disc-like 7 Page 2 of 15

7 Shell larger, breadth 5 - 7 mm; height and breadth about equal; not glossy; umbilicus deep but not wide (hab: RH, L, S, P, C, G ) (stat: W ) Valvata piscinalis (Mull.) Valve Snail

..... Shell smaller, breadth 3.5—4 mm; about twice as broad as high; glossy; umbilicus wide and deep (hab: G )(stat: R2 ) Valvata macrostoma Steenbuch 8(5) Operculum rather calcified, with concentric lines, and not 9 retractible beyond the aperture of the shell; at least 6 mm high and 4 mm broad; fresh water BITHYNIA

..... Operculum horny, with a spiral line, and retractible within the 10 shell beyond the aperture; dimensions less except occasionally in the brackish-water species Sabanaea ulvae; most in brackish water

9 Larger species, height 9.5—15 mm, breadth 6—8.5 mm; whorls 5—6, not tumid or high-shouldered; suture shallow; umbilicus almost completely closed (hab: RH, L , S, P, C, G ) ( stat: W ) Bithynia tentaculata (Linn.)

..... Smaller species, height 6-6.5 mm, breadth 4—4.5 mm; 4—5 tumid high-shouldered whorls separated by a deep suture; umbilicus open (hab: RH, L , S, P, C, G ) ( stat: L ) Bithynia leachii (Sheppard)

10 Eyes borne at the end of tentacles; gill rudimentary, respiration (8) by means of lung; shell conical, rather broad in proportion to height, sides straight in outline, the curvature of the whorls being flattened and the suture shallow; (whorls 6.5—7; umbilicus closed or nearly so; aperture pointed at the top) (hab: B )(stat: L ) grayana Fleming a, Bithynia tentaculata b, Bithynia leachi c, Valvata piscinalis

..... Eyes borne on tubercles at the base of the tentacles; gill present 11 d, Marstoniopsis insubrica e, f, Valvata macrostoma (but not protrusible); shell of other shape Page 3 of 15

11 Relatively shorter and broader; (umbilicus open) AMNICOLA 12

..... Relatively taller and narrower

SABANAEA and 13 12 Larger, height 4 mm; apex pointed; brackish water; (5—6 rather tumid whorls separated by a deep suture; aperture nearly half as high as the shell) (hab: B )(stat: R1 )

Mercuria anatina Swollen Spire Shell

former name Pseudamnicola confusa (Frau.) ..... Smaller, height 2.5—3 mm; apex blunt; fresh water; (4 high- shouldered whorls separated by a deep suture); (see Page 3) (hab: RH, C )(stat: R3 ) Marstoniopsis insubrica (Schmidt) former name Marstoniopsis scholtzi

13 Curvature of whorls slight, suture shallow; aperture pointed at (11) the top; (umbilicus very narrow; body dull white to nearly black; tentacles dull white or yellowish with a black spot or bar near the tip) (hab: B )(stat: W ) ulvae (Pennant) Layer Spire Shell former name Hydrobia ulvae (Pennant)

..... Curvature of whorls more pronounced, suture deep; aperture rounded at the top 14

14 Whorls 5.5 shell somewhat thick-set, the last large; umbilicus closed; body pale grey; tentacles slightly tapering and uniformly pale; some specimens with a keel in the middle of the whorls, and this may be produced into spines. (hab: U )(stat: W ) Potamopyrgus antipodarum (Smith) Jenkins’ Spire Shell former name Potamopyrgus jenkinsi a, Potamopyrgus antipodarum b, Mercuria anatina ..... Whorls 6—7; shell slender, last whorl proportionately not so c, Potamopyrgus antipodarum with keel d, large (except in var. ovala); umbilicus open though it may be e, Ventrosia ventrosa narrow; body dark grey to black; tentacles not tapering and marked with black and grey rings; never with a keel in the middle of the whorls (hab: B )(stat: L ) Ventrosia ventrosa (Mont.) former name Hydrobia ventrosa Page 4 of 15

15 Shell limpet-like, with no obvious trace of helical winding 16 (1) ANCYLUS and ANCYLASTRUM

..... Shell helically wound, or coiled 17

16 Shell taller; length less than twice breadth; the apex almost median; anal and genital openings on the left side (hab: R, L , S )(stat: W ) Ancylus fluviatilis (Mull.) River Limpet .)

..... Shell depressed; length twice breadth or more; the apex inclined 16A to the left or right; anal and genital openings on the right side.

16A Slightly larger species. If you look at the apex with the spire nearest you the apex/spire is twisted to your left, more angular. (hab: L , P, C, G )(stat: W ) Acroloxus lacustris (Linn.) Lake Limpet

..... Slightly smaller species. If you look at the apex with the spire nearest you the apex/spire is twisted to your right, slightly more rounded. Habitats as Acroloxus i.e. lentic (still waters). Often found in garden ponds. (hab: L , P, C, G )(stat: ? ) Ferrissia clessiniana (Mirolli) Introduced American Lake Limpet former name Ferrissia wautieri

17 Shell not coiled in one plane; spire usually projecting above the 18 (15) last whorl a: Acroloxus lacustris b: Ancylus fluviatilis c: Ferrissia clessiniana ..... Shell flat, much broader than high, coiled nearly in one plane; 31 spire not or scarcely projecting above the last whorl, often sunk below it PLANORBIS and SEGMENTINA

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18 Aperture with internal teeth or folds (see Page 15) 44

..... Aperture simple 19

19 Eyes at the tip of the second pair of tentacles 20

..... Eyes on slight protuberances at the base of the single pair of 21 tentacles

20 Shell broader than high; flattened though not to the same extent as Planorbis (Pages 11—14); in outline the upper surface slopes gently to an obtuse point, and the aperture is below the ZONITOIDES

..... Shell higher than broad; whorls rapidly enlarging; superficially c: Zonitoides nitidus d: Succinea putris like a Lymnaea (Pages. 8—10), but with a characteristic pear- shaped aperture pointed at the top SUCCINEA

The snails of the genera Zonitoides and Succinea are not truly aquatic. One of the two species of Zonitoides (Z. nitidus (Mull.)) lives at the base of plants in marshy places and is sometimes found submerged. Two or three of the five species of Succinea may be swept into the pond net from the aerial part of emergent aquatic plants.

21 Shell sinistral, i.e. if it be held so that the observer is looking 22 (19) into the aperture with the spire upwards, the aperture is towards the observer’s left; tentacles thin and awl-shaped; (shell thin; umbilicus absent) PHYSA and APLECTA

..... Shell dextral (though in some species occasional sinistral 25 examples are encountered); tentacles broad and triangular

LYMNAEA and MYXAS

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22 Shell elongate and pointed, the height of the aperture only a little greater than half the total height of the shell; no finger- like processes from the body; (shell thin and shiny) (hab: P, G, T )(stat: L ) Aplexa hypnorum (Linn.) Moss Bladder Snail former name Physa hypnorum

..... Shell more globose, the height of the aperture well over half the 23 total height of the shell; finger-like processes from the body partly covering the shell when the is extended

23 Smaller species, height about 12 mm, breadth 6 – 7.5 mm; shell ovate and fragile; spire short and apex rounded; (shell shiny; second part of the penis sheath twice as long as the first) (hab: U )(stat: W ) Physa fontinalis (Linn.) Fountain Bladder Snail

..... Species of rather variable size, but often larger; shell more rounded and 24 less fragile; spire longer and more pointed

24 Body whorl somewhat rhomboidal; apex narrowly pointed; shell pale; a slight white thickening running round the inside of the mouth; (second part of the penis sheath shorter than the first; height 10—17 mm, breadth 7—10 mm) (hab: U )(stat: W ) Physella acuta (Drap.) Pointed Bladder Snail

..... Body whorl more rounded; apex obtusely pointed; shell more deeply coloured; a slight brown thickening running round the inside of the mouth; (height 9—17 mm, breadth 5—11 mm) (hab: U )(stat: W ) Physa heterostropha (Say) a: Aplexa hypnorum b: Physa fontinalis The last two are introduced, P. heterostropha being American, c: Physa heterostropha d: Physella acuta and P. acuta a Mediterranean species often found in hot house tanks or ponds warmed by the condenser water from factories. P. heterostropha has now been deleted from the British list and is now considered a junior of P. acuta. (Feb 2006)

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25 With a tall spire, nearly as long as or longer than the aperture; 26 (21) second part of penis sheath shorter than the first; (spermatheca with a long duct)

..... With a short spire, much shorter than the aperture; second part 29 of penis sheath longer than the first. 26 Large species, height 35—50 mm, breadth 18—28 mm; spire acute and elongate; last whorl very large so that in outline the side of the shell is concave; shell rather fragile and pale horn- coloured; (shell with fine longitudinal striations and often with widely separated spiral ridges; spermatheca small, ovoid, with a long duct) (hab: L , P, C, G )(stat: W )

Lymnaea stagnalis (Linn.) Great Pond Snail ..... Medium-sized or small species, height up to 25 mm; spire less 27 acute and elongate; last whorl not very large so that in outline

the side of the shell is flat or slightly convex; colour darker 27 Shell elongate; aperture small, about 1/3 height of shell; shell not tapering evenly, the lower half being almost cylindrical; outline distinctly convex in consequence; (height 14—25 mm, breadth 4—7 mm; shell with fine longitudinal striations) (hab: P, T )(stat: R2 ) Omphiscola glabra (Mull.) Mud Snail

former name Lymnaea glabra

..... Shell less elongate; aperture about half height of shell; tapering evenly 28

to the apex; outline just convex 28 Medium-sized species, height 19 - 24 mm, breadth 8 - 11 mm; curvature of whorls rather flattened and suture shallow; lip of the aperture laid back against the body whorl so as to close the umbilicus; shell thick, usually with strong longitudinal & spiral sculpturing; dark reddish brown (hab: U )(stat: W ) Stagnicola palustris (Mull.) Marsh Snail Former name Lymnaea palustris

..... Small species, height 8 -12 mm, breadth 4 - 6 mm; whorls tumid, somewhat flattened on top, suture deep, shell with a characteristic turreted outline; umbilicus open; shell rather thin, a: Lymnaea stagnalis b: Galba truncatula fine longitudinal striations; light brownish horn colour c: Omphiscola glabra d: Stagnicola palustris (hab: S, P, G, T )(stat: W ) Galba truncatula (Mull.) Dwarf Pond Snail former name Lymnaea truncatula Page 8 of 15

29 Shell very thin, transparent, and amber-coloured; spire very short and blunt; when the animal is expanded the body covers the shell almost completely; (spermatheca with a long duct; second part of the penis sheath 1.25 — 1.5 times as long as the first) (hab: RH, L, C )(stat: R1 ) Myxas glutinosa (Mull.) Glutinous Snail

..... Shell usually thicker, not transparent, pale horn-coloured; spire 30 usually somewhat longer and pointed; body not extending over the shell when the animal is extended

30 Last whorl rapidly expanding into a large ear-shaped aperture with the margin usually reflexed outwards; upper edge of the aperture making a right angle with the body; spire short but sharply pointed; shell carried with the spire pointing to the side. Spermatheca with a duct several times longer than the bladder. (hab: RH, L, P, C )(stat: W ) Radix auricularla (Linn.) Ear Pond Snail former name Lymnaea auricularia

..... Last whorl usually less expanded with the margin usually not reflexed outwards; upper edge of the aperture usually meeting the body at less than a right angle; spire less sharply pointed; shell carried with the spire pointing aft. Spermatheca with a very short duct. (hab: U)(stat: W ) Radix balthica (Mull.) Wandering Snail Former name Lymnaea peregra

The species is very variable. Ellis (1926) lists 23 varieties based on small differences in shell shape. Of particular interest are involute from south-west Ireland, and burnetti from Loch Skene, Dumfriesshire, for they may breed true in pure culture (see Page 10). For a discussion of their status, which is beyond the scope of the present publication, the reader is referred to Boycott et al. (1932), Boycott (1938) and Diver et al. (1939). The first of these papers is well illustrated with line a: Radix balthica an obtuse form from Windermere drawings and the second with photographs. b: R. balthica acuminate form from Hampshire For taxonomic reasons the name was changed to Radix balthica in c: Myxas glutinosa d: Radix auricularia Nov. 2005 Page 9 of 15

Stagnicola catascopium ( Say) Former name Lymnaea catascopium

This is an American species which has recently become established in a warm engine-pond in a timber yard at Leith (Kevan 1943). As it is so restricted and as it exhibits a remarkable degree of variation and is therefore difficult to separate simply from the other species, it has been omitted from the key. When its spire is long it resembles S. palustris, and when its spire is short it resembles R. balthica. Differences between the three are shown in table 1 Page 10 shows a typical shell, but for a full series of illustrations of the various forms reference must be made to Kevan (1943).

TABLE I Distinguishing features of Stagnicola palustris, S. catascopium, and R. peregra.

S. palustris S. catascopium R. balthica Shell rather heavy and rather light so that as in S. catascopium sculpture often with both shell is somewhat transverse and shiny longitudinal ridges

Body dark grey or black with white grey or brownish markings greenish with black spots, these on the with black and and yellow spots; no sole of the foot yellowish spots; no spots on the sole of spots on sole of foot the foot Tentacles rather long and similar to S. short and blunt pointed palustris but more pointed and slightly curved Spermathecal long long short duct

a: Stagnicola catascopium b: R. balthica burnetti c: R. balthica involuta d: Radix balthica a rhomboidal form from Hampshire e: Radix balthica an acuminate form from Westmorland Page 10 of 15

31 Very large, shell reaching a height of 12 mm, and a breadth of (17) 28 mm; young stages taller than broad; (edge rounded, no trace of a keel; brownish or olive-coloured) (hab: RH, L, P, C, G )(stat: W ) Planorbarius corneus (Linn.) Great Ramshorn former name Planorbis corneus L.

..... Much less tall and not so broad 32

32 Whorls traversed by strong curved ridges placed at regular intervals and often produced into points at the periphery, examine a range of shells as some may exhibit reduced shell sculpturing; aperture somewhat below the remaining whorls; very small, less than 3 mm broad (hab: RH, L , S, P, C, G )(stat: W ) Gyraulus crista (Linn.) Nautilus Ramshorn former name Armiger crista

..... Whorls without transverse ridges; aperture and remaining 33 whorls more or less in one plane

33 Whorls taller than broad, 7—8 in number and very tightly coiled; (shell brownish or olive-coloured; whorls overlapping on under surface) (hab: R, L , S, P, C, G )(stat: W ) Bathyomphalus contortus (Linn.) former name Planorbis contortus

..... Whorls not taller than broad and not tightly coiled 34

34 Shell tapering towards the edges when viewed in profile, so that 35 it has the shape of a lens; each whorl embracing the preceding (see page 12); (smooth and glossy)

..... Shell not of this shape in profile, the margin keeled, bluntly 36 angled, or evenly rounded; each whorl not or scarcely embracing the preceding

Note: There is disagreement among authorities as to whether the shells of Planorbis, Segmentina etc. are dextral or sinistral; it seems to be most a: Planorbarius corneus b: Bathyomphalus contortus convenient to refer to the side which is uppermost when the animal is crawling c: Gyraulus crista along as the upper side. Therefore the drawing on right shows the upper surface of B. contortus on the left, and the under surface on the right. Page 11 of 15

35 Rather flat; almost equally convex on both sides; without internal septa (hab: RH, S, P, C, G )(stat: W ) Hippeutis complanatus (Linn.) Flat Ramshorn Less flat; more convex above than below; inside of shell divided into incompletely separate chambers by lamellae which show through the shell as white lines (hab: G, P )(stat: R1 )

..... Segmentina nitida (Mull.) Shiny Ramshorn former name Hippeutis nitida

36 Rather large species, usually exceeding 10 mm in diameter; 37 (34) margin nearly always with a flat, blade-like keel; whorls increasing rather rapidly in breadth

..... Without the above combination of characters 38

37 Keel, which is sometimes reduced, towards the under margin of the shell; edge of shell rounded; aperture rather round; greatest breadth of last whorl about 1/4 total breadth of shell; not glossy; breadth up to 18 mm (hab: U, except T )(stat: W ) Planorbis planorbis (Linn.) The Ramshorn

..... Keel near the middle line; edge of shell somewhat tapering; aperture oval; greatest breadth of last whorl about 1/3 total breadth of shell; glossy; breadth up to 14 mm (hab: RH, L , P, C )(stat: W ) Planorbis carinatus ( Mull.) Keeled Ramshorn

38 Whorls 5 or more, increasing rather slowly in size (see page 13) 39 (36)

..... Whorls 5 or less, increasing more rapidly in size (see page 14) 41

a: Segmentina nitida b: Hippeutis complanatus c: Planorbis planorbis d: Planorbis carinatus

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39 Height greater relative to breadth, e.g. at height 1.5 mm, breadth 5 —7 mm; whorls round or slightly angled towards the under side; aperture more or less round; (whorls 6; breadth 5—7 mm) (hab: P, G, T )(stat: W ) Anisus leucostoma ( Millet) Button Ramshorn

A. leucostoma is a slum dweller, grotty not lush habitats, temporary

waters, ditches. No keel, rounded. (Ian Killeen pers. Comm. 1992)

..... Height less relative to breadth, e.g. at height 1.5 mm, breadth 40 8—10 mm; whorls distinctly angled or even keeled; aperture somewhat elongate

40 Larger species, height 1.5 - 2 mm, breadth 8 – 10 mm; whorls 6—8, angled or keeled towards the lower margin; aperture not

set obliquely

(hab: RH, L , S, P, C, G )(stat: W ) Anisus vortex (Linn.) Whirlpool Ramshorn

..... Much more the commoner of the 2 species, in poorer conditions keel is less noticeable than in A. vorticulus . Easy to tell apart if seen together (Ian Killeen pers. Comm.) Smaller species, height under 1 mm, breadth 3.5 - 5 mm; whorls 5, angled or keeled towards the middle; aperture set obliquely (hab: P, G )(stat: R2 ) Anisus vorticulus Troschel

The curvature of A. vorticulus shown opposite is not typical; the other species may be curved like this and A. vorticulus may be straight. Much rarer Very distinctive & larger than stated here. Also distinctive sculpturing – little ribs that expand with the whorls. Likes lush conditions & very good habitats. Medial keel is very noticeable. (Ian Killeen pers. Comm. 1992)

a, b: Anisus leucostoma c: Anisus vorticulus d: Anisus vortex

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41 With a distinct keel; (3.5 - 4 whorls, slightly flattened above; no spiral striae; with a characteristic waxy gloss; upper surface convex; aperture oval) (hab: RH, S )(stat: R2 ) Gyraulus acronicus (Fér.) former name Planorbis acronicus

..... Without a distinct keel 42

42 Whorls 3, bluntly angled towards the upper edge; aperture much expanded and somewhat oblique; lower surface of shell deeply sunk (hab: L , C )(stat: R ) Menetus dilatatus (Gould) Trumpet Ramshorn former name Planorbis dilatatus

..... Whorls more than 3, rounded; aperture not much expanded; 43 lower surface of shell not deeply sunk

43 Shell dull white with spiral striae in addition to the transverse growth lines; aperture rather large, seen from above it meets the preceding whorl at an obtuse angle (hab: U )(stat: W ) Gyraulus albus ( Mull.) White Ramshorn former name Planorbis albus

..... Shell glossy and pale horn-coloured, without spiral striae; aperture smaller, seen from above it meets the preceding whorl at a less obtuse angle, almost a right angle (hab: L , S, P )(stat: L ) Gyraulus laevis (Alder) Smooth Ramshorn . former name Planorbis laevis a: Gyraulus acronicus b: Menetus dilatatus c: Gyraulus albus d: Gyraulus laevis

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44 Eyes at the tip of the tentacles; shell short, broad and globose; apex blunt; (aperture with 4 to 5 teeth) Vertigo None of the seven species of this genus is truly aquatic, but some live on reeds, etc. in marshy places, often above standing water, and so may turn up in the pond net.

..... Eyes behind the tentacles; shell more elongate and conical 45

45 Aperture not much taller than broad; body whorl making up about two-thirds of the total length of the shell; very small, height about 2 mm; (three teeth; five somewhat tumid whorls; shell thin and whitish) Carychium The Herald Snail

The two species of this genus are not truly aquatic but occur in moist situations among dead leaves, etc. With the next two genera they complete the family Ellobiidae.

..... Aperture much taller than broad; body whorl making up about 46 three quarters of the total length of the shell

46 Shell thick and white; two ridges or teeth inside aperture on a: Vertigo b: Leucophytia bidentata c: Ovatella myosotis inner wall; height up to 6 mm Leucophytia bidentata (Mont.) This snail lives on the sea-shore just below high-water mark, and it is included here because it might be confused with the next species which is estuarine.

..... Shell thinner, brown or yellowish; inside of aperture armed as in the preceding but, in addition, on the outer wall a thickening which may bear one to several tubercles or teeth, and sometimes on the inner wall a third tooth or ridge; height up to 8 mm Ovatella myosotis (Drap.) former name Phytia myosotis (Drap.)

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