ZO 591 Biology of Mollusca (Taylor)

0 Spring 1968

Kay to Major families of Morth American freshwater snails,

by external charastess of living animals

1f2). Hind end of foot bearing a horny that closes of shell. Head and foot sepasated by a deep cleft, in front of which is an elongate, transversely wrinkled, mobile rostrum snout)

Eyes lateral to, or on, long axis of tentacles. Tentacles tapering

and slender. Feces extruded as discrete pellets or as dorsally

grooved, ragged-ended ropes. Shell low-spired to high-spired,

almost always dextral. SUBCLASS PROSOBRANCHIA 2(1) Hind end of foot bearing no horny operculum that closes aperture of shell, Head and foot closely united, with no elongate ea um

(snout) in front of foot. Eyes between bases of tentacles.

Tentacles flat and triangular or tapering and slender. Feces

extruded as smooth, ragged-ended ropes. Shell -like,

discoidal, or high-spired; sinistral or dextsal. SUBCLASS

EUTRYNEURA, ORDER BASOMMATOPHORA . 0 0 0 • 0 0 0 0 17 , 3(4) Operculum multisplral, consisting of numerous equall) wide

overlapping spiral bands. Eyes in the middle of the tentacular

bases, on long axis of the tentacle in dorsal view. A ctenidium with lamellae on both sides of a central blade 'isipectinate ctenidlum) projects anteriorly from the cavity. A cili- ated pallIal tentacle projects from the upper right corner of

the aperture. Rostrum with parallel sides, slightly expanded

at the end; terminal pads not set off by a na-row groove. Widest

part of foot at the front, where two narrow, tapering lobes curve 2

laterally and then posteriorly. Widest part of foot behind

anterior lobes is clearly in the posterior half of the foot.

Anterior pedal groove wide, deep, and V-shaped, so that upper

edge of foot below rostrum is posterior to front edge of sole.

Feces extruded as dorsally grooved nagged-ended ropes. Shell

low-spired to moderately high-spired, less than 10 mm high.

Superorder ECTOBRANCHIA, family Valvatidae.

4(3) Operculom concentric; or consistfng of only 3 or 4 spiral tU7nS.

Eyes on cute:- bases of tentacles (or rarely on short peduacles

if tentacles are absent). Ctenidium Internal, not projecting

from mantle cavity, consisting of many triangular lamellae that

hang from the roof of the mantle cavity (monopectinate ctenidium.

No pallial tentacle projecting well outside the shell. Rostrum

tapering toward the front; terminal pads may or may not be ex-

panded beyond width of rost.-um, usually set off by a narrow

groove. Front corners of foot expanded into short lobes that

project laterally; these are no wider than the greater part of

the foot, or are only slightly wider. Most of the foot behind

anterior lobes of equal width. Anterior pedal groove narrow, of

equal width across the edge of the foot. Feces extruded as

ditcrete ovoid or spindle-shaped pellets. Shell discoidal to

high-spired, minute to large (1 mm to about 100 mm long in

adults). Superorder PECT1NI8RANCHIA, Order TAERIOALOSSA . . 5

56) External color pattern splotched, mottled, marbled or YO legated;

yellow or orange pigment gi-anules usually present. Shell 10-100

mm long in adults, globose, conical, or discoidal. Operculum 3 calcareous or corneous, concentric or spiral. Nuchai lobes acting as inhalant and exhalant siphons may be vesent. Male

may lack a penis; or have penis in the right tentacle, or in

the roof of the mantle cavity, or (rarely) on the floor of the

cavity. Reproduction ovoviviparous or oviparous; female may

have brood pouch on back of head, or oviducal groove on right

side of body.•.• —•.•.•.• 0 , 0 0 0 . . 7 6(5) External color absent, faint, uniform, or in simpie patterns; no fine networks or marbling or mottling; usually no pigment except

melanin. Shell less than 10 mm long in adults, tueriform, globose, conical or discoidal. Operculum corneous, spiral. No nuchal lobes. Male with copulatory organ (verge on the

floor of the mantle cavity. Reproduction ovoviviparous or

oviparous; female does not have brood pouch on back of head or

oviducal groove on right side of body. Super7amily RiSSOACEA 15 7(8) External color pattern splotched, from irregula clusters of yellow or orange pigment granules. Operculum calcareous or Corneous, concentric or concentric around a small spiral nucleus. Nuchal lobes acting as inhalant and exhalant siphons present.

Floor of mantle cavity divided lengthwise by a vertical lamella

epitaenia). Male with penis, variously located. Female without oviducal groove; if ovoviviparous with young in the pal Hal ovi-

duct at the right side of the mantle cavity. Shell conical

giobose, or discoidal, 10-100 mm long in adults, plain-colored or spirally banded. Feces are ovoid OF apindle-shaped pellet with internal spiral structure. Superfamliy V ViPARACEA 0 If

8(7) External color pattern, mottled, marbled, or variegated.

Operculum corneous, spiral. No nuchal lobes or epitaenia.

Male lacks penis. In female a groove (oviducal groove) descends

right side of body stalk to sole, or there is a brood pouch con-

taining young on the back of the head. Shell turriform, may

exceed 15-25 mm in length, often banded, spirally or irregularly

splotched. Feces are spindle-shaped pellets, non-spiral in

structure. Superfamlly CERITHIACEA ...... 13

9(10) Operculum corneous. Shell plain-colored or with spiral bands,

20-100 mm long in adults. Eyes op short peduncles, lateral to

tentacles or fused with lateral aspect of tentacles, not in low

swellings on lateral bases of tentacles. Penis present in roles,

either in right tentacle or on roof of mantle cavity, not on

floor of mantle cavity. Feces are ovoid pellets voided as a

group ...... 11

10(9) Operculum calcareous, concentric. Shell without bands, 10-15 mm

long in adults, conical, dextral. Eyes In low swellings on

lateral bases of tentacles. Copulatory organ on floor of mantle

cavity to right of midline; it is a verge with single accessory

process (inclluding a duct) on the left side. Feces are spindle-

shaped pellets, of spiral construction, voided singly or in

series, not in a group. Reproduction oviparous; eggs laid in a

double row of adjacent capsules. Family Bithynildae.

11(12) Operculum corneous and concentric, or concentric around a small

spiral nucleus. Shell conical, usually dextral, rarely sinistral;

25-100 mm long in adults; plain-colored or with 3-4 spiral brown

bands separated by approximately equal interspaces. Rostrum 0

, , ..-, simple:, .:- i nf2: t. :crc.:1 tcnt ics. E ‘,. CS. C.;') •'' ..:":'''1. •.'C'..11: .:...::::-.TI

:ftsc.:.- '..,:it ftterc:A ,7s::cct. 0;.'- tclt,-,:c:Ics. Tentcics stit,

tacrinp; E's,,:;,. trie,171 in fi.alios; pcnis In rii.,t- tc.: ',-,D- o

is then thic a',-6 rc:curveC K:steriorly. re:c:uctif2,n. ,..:.v- ..:n/I-,.

viparous. W> lunzf. Fc,mily Vivilricl.ce..

12(1 .1). Opercuium corncous, concentric. Sell 0obose or disoia:,

.de:aral; about 50-75 mm icing In ceults; ploin-colored or ‘-'ith

1 0-15 spiral brown hands of vc:ricble width se2aated :),,' intcr-

spaces appro:timately equal to width of Wider bands. RostruIIl.

with a. labial tentacle on each side. Eyes on shut peduncles •

lateral to the bases of the tcntacles. Tentacles lorq, sl ner,

mobile; symmetrical. Penis on roof of mantle cavity. fle.-4-o-

duction oviparous; eggs laid out of waters as clusters rxf

calcareous soherules. Part of mantle cavity a ±Ailmonary :,,...c,

with a long siphon. Family Ampullariidae. l3(14) Border of mantle smooth. FCM410 with a groove 0:)vidua1 vor.ve.)

descending right side of body stzik toward sole. llost7..um not •

flattened, oval in crass-section. Shell plain. ;olorcd or ntn

spiral bands. Family Plcuroceridae.

14(13) Border of mantle with several elonozte papilicte. Femr::le ' th

a brood pouch containing live young on back of 'Telle. t: .t.-uli,

flattened dorso-ventrAly, long-eval in cross-sction. Eix:i

often with I rreF;:ularly spotched color pzittorn. 7;:rnfly

150 Eyes on sEcrt pcunelcs; no tentccies. Animei ,-7',Ir-c , -.

Shell conici71, iess nz::n 4 mm long, vnifc.rmiy 1:1 NOun, t.l o c...- -•

c.ercous port cif the .s ciii T.,E.', -c brcn-c..olcred. V,'2,1c 1,,t ,7

• biadc-Iii1;c coul.(ntovy 1,21- - n. (vere) in t:-:(1 i et: c ,-.:F:v.P,:y.. 6

usually just out of water, in s ring-bogs Of beside saline

pools. Family Assimineidae.

16(15) Eyes on low swellings on the outer bases of long tapering

tentacles. Animal pigmentless to lightly or darkly colored,

sometimes with yellow or white granules in addition to melanin.

Shell discoidal, conical, or turriform, 1-10 mm long in adults;

plain-colored, colorless, or (rarely) with spiral bands in the

periostracum; calcareous part of shell always colorless. Mole

with a copulatory organ verge) in the mantle cavity that may

be relatively large or small, simple or with bulky accessory

glands. Habitat almost always in water (fresh or brackish), rarely

Just out of water. Family Hydrobiidae.

17(18) Tentacles short, flattened, triangular in plan. No postvelar

flap at the posterior base of the tentacles. Posterio;- end of

foot rounded. Blood without evident color. Animals monoecious,

with genital openings on eight side of body (i.e., animal

dextral). the male opening beneath the hind end of the right

tentacle and usually hidden in the crease. Superfamily

LYMNAEACEA ...... 19

18(17) Tentacles long and narrow, rod-like. A narrow flap (postvelar

flap) extends posteriorly from the base of each tentacle and

encloses a groove on the lower side. Posterior end of foot

either rounded or acutely pointed. Blood red or without evident

color. Animals monoecious, with genital openings on left side

of body (i.e., animal sinistral); the male opening Just behind

the end of the postvelar flap ...... 0 . 0 . 21 19 '

ar anc.i cvities :

a sir:on. The srtall may air ftto ca7itv, r

ne cavity may be th1.jth wzter cr .a smoli hy Wc.

Family Lymnaeidae.

19) Shell limpet-like, generally ovcr 15 mril longtlhen

open furrow around the head anti foot contains no seconti.ary

or organs of any kind. I hypo lar ezvity or sip!ron. I D

'.ancidae.

2122) Posterior end of foot either reunCed or acutely ., -olnted. IOD

red or without evident color. Cifqes of mantle smoon, not

serrate. OpEning between hypopeplar and Fu/monary cavities

modified into a secondary gill Clseudoloranch); the animal

usually does not take air into the pulmonary cavity. Shell

discoidal, low-spired, or limpet-like; rarely 1; gn

Superfamily PLANORBACEA ...... 23

22(2)) Posterior end of foot acutely pointed. Blood without evlJeni:

color. Edges of man le usually serrate, sometimes smooth, the

mantle covering part of the heIl on the right side. € eri T Ç

bctwccn hyr,pepia,. and ;:ul:zonery cavities modified into Q

siphon with which the snail takes air into its 7,:Amr.-nccy

Shell high-spqred, p:;caring sinistral. Euper7(7mily

Physidae. 8

23(24) Posterio,' end of foot rounded. Blood without evident colo'.

Pseudobranch on left side of body does not protrude beyond

shell; it is a triangular flap with transverse lamellae. Shell

limpet-ilke, generally less than 5 mm long. Family Ancylidae.

24(23) Posterior end of foot either rounded or acutely pointed. Blood

red or without evident color. Tip end of pseudobranch protruding

from the shell on the left side is T-shaped In cross-section.

Shell discoidal or with a spl-e, appearing either dextral

sinistral, 2-30 mm in diameter in adults. Family Planorbidae.