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

94 l\:IOLLUSCA. [CONCHACEA. Foun<l in most water streams, and in stagnant ditches an<l pools, throughout Britain and Ireland; is conunon i1_1 Du<l<lii_1g- ston Loch, near Edinburgh, of the size abov~ described, wluch is considerably more tlian its ordinary <lime11s1011s. This shell is readily distinguished from the C. 1·ivicola, by its more vcntricose shape, in being thinner, more trnnsparent, aml sel<lom measuring above half the size of the former. 3. CYCLAS LACUSTRIS, pi. XXXIX, f. 20. C!Jclas lacust,·is, First E<l., pi. 17, f. 16 ; Drapernau<l, Hist. des Moll., p. 130, pi. 10, f. 6, 7; Lamarck, V, p. 559, No. 3; Tnrton, Man., p. B, f. •1 ; Pfcilfer, p. 122, pi. 5, f. 6, 7 ; Fle- ming, Dril. An., p. 453. Shell thin, rhombic-orbicular, subequilateral, somewhat com- pressed; sides rather obtuse, rendering the general contour more circular than others of the genus; obsoletely striate; beaks obtuse, of a grayish ash-colour. Foun<l in Ulliswater; a small pon<l 011 the grounds at Corby, Cmnberland; ami al Prcstwick Car, Northumbcrland. lt is a raro British shell. It is much more compressed than any of thc other British Cyclydro. 4. CYCLAS CALYCUJ,,\TA, pi. xtxrx, f. 21. C!Jclas cal!Jculatci, First E<l., pi. 17, f. 13; Drapcrnau<l, I-Iist. iles !\foil., p. 130, pi. 10, f. M, 15; Lamarck, V, p. 559, No. 5; Pfcifl'cr, p. l 22, pi. 5, f. 17, 18 ; Turton, Man., p. 14, f. 3 ; Forbc~, p. 50; Cyclcts lacusfris, Al<ler, Mag. Zool. an<l Bot., II, p. 118. Shcll thin, rhombic-orbicular, grnyish ash-colourcd, com- prcsscd, diaphanous, substriatc, or nearly smooth; slightly angular 011 one side; umboncs vcry prominent, an<l acule. Abont a quarler of au inch long ; ami its width nearly the samc. Found in thc lakcs of Wcstmorelan<l, aucl is not uncommon in severa! pits ancl pomls ncar Manchesler, but is a very rare and local species. GENUs 1G.-P1s1D1U)I.-Pfcilfer. Shell eqnirnlve, transvcrse; sides nnequal, completely closing; i11 thc right vall'c onc, ami in the _left valvc two opposite, very small, primary tceth; behind alHI before, two thin, lamellar, side tecth; !hose of I he la11er cleft in the right val ve, in ordcr to rcccive the opposite ones. The shdls of this gcnus are distinguishecl from those of Cyclas, by hcing less equilateral in thcir form, ancl in the liga- mentary sidc hcing shortcst, which is the reverse in Cyclas. l. Pmniu)t 011w1uu)1, pi. XXXIX, f. 22. Pisiclium oblir¡1mm, First E<I., pi. 17, f. 1-1; Cgclas oblir¡1w, Lamarck, V, p. 5,,9, No. '1; Pisidium oblir¡1mm, Pfciffcr, p. J2-l, pi. 5, f. 19, 20; C!Jclas pal11.~/1·is, Drapcrnaud, Hist. des ;1[ol1., P· 131, pi. 10, f. li, IS; Cyclas amnica, Turto11, Brit. Bi1·., p. 250, pi. 11, f. 15; lb., Man., p. 15, f. 5; C!Jclas <mmi- rns, Fleming, !hit. An., p. '153; 1i:lli111t 111n11ica, Gmelin'$ Linn~, I, p. 32-12, No. 7S; illiiller, p. 20;;, No. 3S9; Tellina ,·i,·alis, Linn. Trans., IV, p. 1 S7; Donornn, Brit. Sh., II, pi. Ü·l, f. 2; Cardium. 1mmicum, i\Iontagu, p. SG. Shell thin, subpellucid, of a brownish or grayish horn-colour, obliquely oval, mod<.>rately convex, and sulcatcd concentrically, with thc furrows finely sl.riated; beaks tumicl, a little produccd, ancl placed consi<lerably towar<ls the anterior side; lcft Yalve provicled with a double central tooth, and two lateral tecth on each side, standing parallel one within the other, the outer of which is very small; right valve with two cardinal, appoximating, oblique tecth, with one lateral tooth 011 each side, that 011 the posterior si<le strong, ancl elevated abovc the margin of the shell; inside bluish-white, clim in the disk, but glossy towarcls the margin; on each side are <listinctly visible, large, smooth spaces, to which the musclcs adhere. Length thrce-eighlhs of an inch; breadth half an inch: although it is but rarely mct with of this size. Founcl in slow running rivcrs ancl slreams, ami is known lo inhabit the Avon, \71 7 iltshire; in the water-courses in the mca- clows near vVareham, Dorsctshirc; the Liffey, Irelancl, ncar Sallins, Kildare, an<l in rivulets which run through the bog al that place; we havc also mct wilh it in a strcam, which emptics itself into the Water of Leith, a little way above Colt Bridge, near Edinbmgh; ancl many other localities. 2. P1s1D1UM I'ONl'INALE, pi. XXXIX, f. 23. P isidium.fontinalc, Pfciffer, Land un W as. Sn., p. 126, pi. 5, f. 15, 16; Brown, Eclin. Journ. Nat. an<l Geo. Sciencc, I, p. 11 ami ,113, pi. 1, f. 5, 6, 7; Cyclasjbntiualis, Drapernaud, I-I ist. des l\1011., p. 130, pi. 1O, f. 1 1, 12 ; Lamarck, An. San. Vert., V, p. 559, No. 7; Cyclas pusilla, Turton, Conch. Dict.; l b., Brit. Bi I' ,, p. 251, pi. 11, f. 16, 17 ; lb., Mau., p. 1 G, f. 7 ; P.isidium pulchcllum, J enyns, l\:Ionog., p. 18, pi. 21, f. 1 ; Thompson, Ann. ami Mag. Nat. 1-list., VI, p. 53; Forbcs, Mal. ilion., p. 50. Shell suboval, oblique, very convcx, pellucid, and covercd with extremely fine, concenlric, rather obscure striro; umboncs obtuse, placed ncarest the anterior sidc; hinge with one central ami two lateral teeth in the right rnlve, and two obliquc car- dinal ami one lateral toolh in fhe other; colour pale ash. A littlc more than an eighth of an inch in length ; ami somewhat more in breadth. First cliscovered in a ditch at Duddingston Loch, near Edin- burgh, hy my frien<l James Geranl, Esq. I havc since founcl it in the ditch at the norlh en<l of the Loch, ancl also in a dilch al Hunter's Bog, King's Park. Turton, in his l\fauuel, snys it is found "in most streams ami brooks," but although I have examined numcrous localitics in England, Ircland, ami Scotland, I harn not found it so common as he allcgcs. :3. PISIDIU)[ OllT.USAI.E, pi. XXXIX, f. 2-l. Pisidium oblusali:, Aldcr, Mag. Zoo). ami Bol., ll, p. 11S; Pfciffcr, p. 125, pi. 5, f. 21, 22; Brown, Edin. Journ. Nat. ami Gco. Science, I, p. ,113; Thompson, Ann. al)(l Mag. Nat. I·list., VI, p. 53; C!Jcl<ts obtusafis, Lamarck, V, p. ;;59, No. o; Pe1·a gibba, Lcach, ilISS. Shcll obl ic¡uc, vcntricose, heart-shapccl; sidcs somcwhat 1111e- qual; beaks prominent, all(l ohluscly roundcd; pcllucid, yel- lowish-white, or palo horn-colonrccl; with cxtrcmdy minute, conccntric, thin si ria! ; thc lower edgcs of the 1·alvcs rathcr sharp. Lcnglh an c1gh1h of a11 inch; hrcadth an cighth ami a quarter; thickncss nol qui te an cighth.