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

l\fr Al\!.\,] l\'IOLLUSCA. 109 :1'his spe_cics migl_1l easily_ he mistakcn for thc young of 111. tl'wngulal'is, h 1_1l will ~e d1stinguishccl from thal shcll in bcing lcss angulalecl, ''.' wantmg crcnulations ou the margin, ami its hreadth proportionably greatcr; il is, hcsicles, a considerably ,maller shell. Founcl on lhe eoast of Cornwall, the ,veslern coasts, and in Ireland., Forbes says il inhabits the byssi of l\fodioli from deep water oíl Douglas, Isle of l\fan. GEKUS 3G.-LuTRARIA.-Lamarck. Shell equivalve, inequilateral, lhin, transverscly ovale or oblong; open al bolh sides; lhe posterior side generally the longer, all(I always gaping more lhan the other; one valve wilh two lhin, laminar teelh, one of which is sometimcs compound; ~he oppos!te valve with lhree tecth, the central one compound rn some mstances, and lhe posterior one slcnclcr and com- pressecl; ligmncnl interna!, situatc in a dcltoiclal, oblique, inler- nally projcct.ing, spoon-shapecl pit, with a prominent margin placed ncxt to the teeth in each valvc; two clistant, lateral, muscular impressions; pallial impression with a very large sinns, lying lransversely in most specics. 1. LUTRARIA ELLIPTICA, pi. XLIII, f. 2, 3. Lutrn,·i<i elliptica, First Ed., pi. 12, f. 2, 3; Lamarck, V, p. 468; Turton, p. 65; Forbcs, p. 54 ; L1ttraria vulga1·is, Fle- ming, p. <16•1; Pennant, IV, p. 92, pi. 52, f. 44; Montagu, p. 99 ; Donovan, II, pi. 58. Shell lransversely oblong-ovate, thin, compresscd; Iongcr side with a shallow groorc, emanating from the base of the umbones, :me! terminating on the margin, over which there are sorne inegular stritc-like lines, which whcn the epiclcrmis is remO\•cd, present lhe appearance of being scratchecl by a file; umbones small, placed near to one side; surface with fine, nearly obsolete, irregular, concentric stritc, or groovcs, ami irrcgularly wrinkled transvcrsely, lhese are shallow on the disks, but slronger ancl more decided towards the sicles, coverecl with a prctty strong epidermis, of a drab-colour, rarely approaching to fawn ; sometimes with a fcw indications of lines of growth, and iu some these assume the appearancc of nearly obsolete ridges, particularly towards lhe shortcr side; inside smooth, bluish- whitc; ancl gaping at both sides. Found 011 many of the 13ritish coasts wilh a sancly bottom, e,pecially at the influx of rivcrs. Fig. 3 is a very thick shell, in proportion to its sizc, which I figuree! from the colleclion of Sir Jolm Trevelyan, Bart., at '\,Vallington, Northumberlancl. 2. LUTRARIA SoLENOIDEA, pi. XLIII, f. l. Lutraria Solenoidea, First Ed., pi. 12, f. l ; Lamarck, V, p. 468; Luh·a1·ia oblonga, Turton, Biv., p. 64, pi. 5, f. 6; L1ttra- ?'Ía hians, Fleming, p. 465; Psammophila Sole11oidca, Lcach, MSS., P· 6; llfactra hia11s, Montagu, p. 101; Donovan, III, pi. 140. . . Shell trausvcrsely oblong-ovate, greatly mequ1\atcral; um- bones small, depressed; surface with rugosc, conccntric wrin- kles, which prevail most at the posterior sidc, covered with an opaque, dark brown, thick, dusky epidermis, sometimcs of a redclish tinge; hinge provided with one flaltcned tooth, which is groovcd on thc forc part, ancl locks betwccn two 2E in the opposite valve, thc smallcst of which is clcft; the car- tilage pit is large all(l triangular; insicle smooth, white, with an elcrntcd, transYcrse riclge, situate on the uppcr sicle of the posterior muscular imprcssion; gaping considerably at thc pos- terior side. An extrcmely local spccies, but is said to be not unco1111non al the influx of thc riYer betwcen Truro ami Falmouth, in Cornwall; all(l has becn founcl on thc Dorset coas!. 3. LuTnAnu coMPllESSA, pi. XLIII, f. ,1. Lutiw·ia com.pressa, Firsl Ed., pi. 12, f. 4 ; Lamarck, V, p. ,1G9; Listci·ia com¡J1'essa, Turton, Biv., p. 51, pi. 5, f. l, 2; Aúnt comprcssa, Leach, l\1SS., p. G; ./l'lllphidesma com¡Jl'cssum, Flcming, p. ,132; 11/actm Listen·, Gmclin, p. 32Gl ; 11/actra comp1·cssa, l\fontagu, p. 96 ; Tellina pla11a, Donovan, II, pi. G4, f. l. Shell frans,·ersely subornte ancl subtriangular, thin, brittle, much comprcssecl; umbones not quite cenlrnl, all(l rnlhcr ob- tuse; anterior side wcll rounded; postcl'Íor sidc a little longer than the othcr, and slightly acuminalcd; externa! smfacc of a dull yellowish-white, covered with pretty strong, trans\'Crse stritc-like wrinklcs; cartilage ca\'ity largc, triangular; primary tceth small, a single one which locks into a clcft. looth in thc oppositc vah·e; inside smooth, white, ami rather dull; pallial sinus very large, occ:upying nearly a. half of thc interior surface; margin plain. A common species on most of the Brilish coasts, ami prcrnils at the mouths of rivers. SECTJON IV.-CnASSIPEDES. The mouth unitcd in fronl, or partly so; foot thick, ami situate posteriorly; shclls gaping when closed. FAMII,Y VIII.-MYAI\IA. Shclls wilh a broacl, spoon-like tooth in one or both vah•es; gaping at both extremities; in most instances with an externa( ligament ami interna! carlilage. GEl'rns 37.-TnnACIA~Lcach. Shcll very thin, transverso, inequivalvc, inequilalcral, one vah·e usually more com·ex than the other; umbones gcncrnlly obtuse, ancl subccntral; hingc with a broacl, trans\'crse, fre- quently thickencd toolh in bolh vah•cs, ami an obliquely trian- gular pit in thc centre, in which the cartilage is siluate; surfacc covcrecl with a very thin epidermis; two well-marked, but dis- similar muscular imprcssions in both valves; pallial impression interruptcd by an arcuatcd sinus, at the posterior sidc, which is truncated. l. TIIRACIA DECLIVJS, pi. XLIV, f. 5. Anatina declivis, First Ed., pi. 11, f. 5; Anatina puúescens, Turton, Biv., p. 45, pi. 4, f. 1, 2; Tln-acia declivis, Leach, MSS., p. 5; lllya pttúcscens, Monta.gu, p. 40 ; Donov:m, II, pi. 82; Amphidcsma conve.i·um, Fleming, p. 431. Shell thin, brittle, transverscly oblong-ovate; umboncs largc, vcry obtuse, ancl not quite central, that of the larger valve with a hiatus for thc rcccption of the beak of the othcr valvc, and to pcrmit the opcning of the shcll; posterior si<le rounded;