Illustrations of the recent conchology of Great Britain and Ireland, with the description and localities of all the species, marine, land and fresh water

CLASS SECOND. CONCHIFERA; OR BIVALVES. Animals soft, without articulations, <lestitute of a hea<l or organs of vision, and always fixcd within a DIVALVE shell; providc<l wilh externa) branchi.n, a simple circulation, and an unilocular heart. Ali the species are aquatic, living eithcr in thc sea or frcsh water. Nonc of the animals have an interna) sheU. The body is invariably soft, and thc mouth is situate<l ncar the lcft si<le of thc hingc. Sun-D1v1s10N I. Ligamcnt nonc or unknown, or in its s tca<l a tcn<linous chord, which supports thc sheU. ORDEll I.-MONOMYARIA. Animals providccl with but one muscle of attachmcnt, or ad- ductor musclc, which )caves one subcentral muscular imprcssion insi<lc of cach valvc. FAMII.Y I.-BnAc111orooA, Shcll hirnlvc, adhering to cxtrancous marine bodics, cithcr by thc shc11 itsclf, being in contact with them, or attached by a tcndinous chord. Shclls not quite equivalvc, an<l open by a hingc. GENUS 1.-TEnEBRATULA.-Druguicrc. Shcll inequivalve, equilateral, generally trigonal and gibbous; atlachcd by a short pecluuclc to cxtraneous marine bodics; thc larger, or upper valvc, with a projecting umbo, frcquently bcnt, ali(! perforated at its apcx, or notchccl at its inner edge, an<l haviug a small curvcd looth on cach side of its hingc, which fits into a corresponcling pit in thc opposite 1·alrc; thc insiclc of thc smaller valvc is provirled with two slender testaceous processes, which are somclimcs simple, short, and recurvccl, at others con- sidcrably clongated, branchcd, bent in ,·arious dircctions, ami anastomosiug for the most j,art; somctimes thcy are siluate near thc centre of thc vah-e, ami in othcr instanccs are united by thcir points to thc shcll; thcsc usually emanatc from each siclc of the h ingc ; both rnh•es are pro,·ided with two ncarly obsolete, muscular impressions, but sometimcs thcy are strongly developed; those of the larger, or perforatcd rnlvc, are oblong, central, alHI close to cach othcr; in the smaller vah-c thcy are triangular, with their anglcs rounded, also ncarly central, but more distant titan in the other ,·al\'c. l. TE!lEllllATULA CHANIU~t, pi. XXII, f. 10, 11, 12. 1'ei·cbmtula cm11i11m, First Ed., pi. 3-1, f. 10, 11, 12; l\í(illcr, Prod., p. 24!); lb., Zoo!. Dun., pi. 84, f. 1; Fleming, Phi). Zoo!., II, p. •l!)S, pi. 4, f. 4; lb., Ilrit. An., p. 368; Tcrcbm- t-ulc, vitrca, Fleming, E<lin. Ency., VII, p. 96; lVIontaga, Linn. T rans., p. 288, pi. 13, f. 2 D; Anomic, cranium, Brown, Ency. Brit., VI, p. 422 ; Turton, Div., p. 236. Shell ventricose, front margin slightly truncatcd, semi traus- parent, brownish-white, with the externa) surface fincly and dclicatcly shagrcened, which can only be seen by thc aicl of a strong lens, ancl slightly and irregularly wrinklcd conccntrica11y; largcr valve with bifid lateral tecth; those of t.hc smaller valve, with a small, horizontally projecting tooth, from which emanatc two projccting processes, upwarcls of threc-fourths across thc shell ; providecl with a simple pccluncle. Foun<l in <lcep water al Bressay, Zetland, by Dr. Flmning; ami a single specimcn was clrcclged alivc.: in Dublin Bay, which is now in the Museum of thc Dublin Socicty. 2. TEREIIRATULA AUR11'A, pi. XXII, f. 13, 14, 15. Tc1·cbmtula am·ita, First E<l., pi. 34·, f. 13, 14, 15; Flcming, Phil. Zool., 11, p. 498, pi. 4, f. 5; l b., 13rit. An., p. 369; Tc1·c- bmtula coslata, Lowc, Zool. Journ., 11, p. 105, pi. 5, f. S, !). Shell rather thin, scmitransparcnt, ancl compressccl ; narrow at the summit, suddcnly widening as it clcscen<ls, and tcrmi- nating in a well roundcd basal margin; uppcr rnlve ílattish, semicorclate, and incquilateral; bcak slightly pro<luccd, a little rounded, and horizontally lruncatcd, for tite rcception of the perforation, which is large, and completccl by thc pointed umbo of thc lowcr, or smaller valve; lower valve somcwhat rounded, a little deprcsscd, with a slight central clc\'alion; both rnlves cove:rc<l cxternally with regular, longitudinal, divergent, some- what scabrous ribs, which are interrnpted by a fcw irregular, incquidistant lincs of growth, producing a scaly or vaultcd ap- pcarance; margin of the valres rcgularly roundcd ancl toothe<l, but dcstitutc of any sinuosity ; colour an obscuro reclclish-brown towards thc beaks, which becomcs lcss intense as it di rnrgcs towards thc margins; inncr surface minutely punc(ated, pale yellowish, or cream-coloured white; pedunclc short, consisting of numerous, uncqual, tubular fllaments, attached to a compli- catcd tcndino-muscular apparalus, and chielly to tite lower vah·e. Lcngth somcwhat more !han t hree-tenths of an inch; breadth rathcr lcss. DiscoYered by i\I. J. Berkeley, Esq., allached to (he undc r siclo of a rock, on the l>cach near thc Custom H ouse, Oban, al a Yery low ticle. A specimcn was scnt to me, fro 111 thc samc locality, by Captain Cannichael; allCI Dr. Flcming found it in Ullapool, Loch Broom. 3. Ti::1mnnATULA PSITTACEA, pi. XLVI, f. 2, 3, ·l. Te1·cú1·a/11la psittacea, Firsl Ecl., pi. 1O;'' f. 2, :l, ,t ; Turton, Conch. Dict., p. r,, pi. 11, f. -12; lb., Brit. Bil'., p. 2:lü. Shcll oval, com·cx, of a clark horn-colonr; bcaks grca1ly pro- dncecl, a1HI cnned; superior margiu 111ul11latcd; , idcs ahruptly turned inwards, clcprcsscd, ami pro,·idccl wilh a fcw longitndinal stri..c; fron l margi n sonicwhat imlcntccl 011 both sidc:;, aud pro-