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

PnOLADARIA.] MOLLUSCA. 115 confidcncc assert that no t wo spccies of thc samc genus are 111ol'c dissimilar atl(\ 1listincl in thcir essential characters. Indc- pendcntly of thc total want of the ring, a1HI thc large frontal gapc, thc smallcr cm\ is ronm\cd, a1Hl 11ot as in thc lasl spccies trnncale, a1HI it has no acccssol'ial \'ah-es. In aclclition, also, to thc othcr marks of discrimination, it 111ay be obscn·ed, thal thc ,·al\'cs of thc Plwlas papy1·ace<1 are closecl in fronl by a fine clastic mcmbranc, in thc middlc of which, near thc base or rontl(lcd cxtrcmity, is a small oriílce or spiraclc, which can be closcd al plcasurc, ancl thro11gh which water is oflen cjected." side of thesc is place<! a long, spatuliform, plate-like, accessorial \'al\'e, aílixed by the connecting membrane; anterior sicle of the vah-cs with rough, transrnrsc, spinous strirc, terminaling in a rouncled beak, with a large gape at that sidc; posterior si<le smooth, marked with li nes of growth, ami terminating obtusely; externa! surface oí an ochrc-colour, but varying accorcling to thc colour of the substance in which it locales; inside smooth, white; below the umboncs, a large, ílat, cun·ed tooth. -t. PIIOLAS SULCATA, pi. XLVIII, f. 17, IS. Plwlas sulcata, Firsl Ed., pi.!), f. 17, 18. Shcll trans\'crsely oblong-ovatc; hinge line nearly parallel; almosl cqnally rounclcd al both cxlremities; a thickening and slight llexure 011 the superior margin, extending lo the anterior ;ic\e; from thc umbonal region emanate two obliquely longitu- dinal, narrow furrows, ami terminate on lhe basal margin, al which poinl the shell is longesl; anterior to thc sulci, the sur- face is covered with close-set, wavecl, transverse slrioo; ami the posterior side with irregular, broken, concentric strioo; externa! surface of a yellowish or pale brown hue; insi<le smooth, white, a cuncd, ílattcne<l, tooth-like pl'ocess under the umbones, a small denticle al the central point of the umbonal region, ancl an obliquc, longitudinal rib, correspon<ling to the externa! furrows. This shell was foun<l al Dunhar, and is in the collection of David Falconer, Esq., of Cal'lowrie. 5. Pnot.AS TUUERCUl,ATA, pi. XLIX, f. 12, 13. Pholas tuberculata, Turtou, Bi1•., p. 5, pi. 1, f. 7, 8. Shell transl"ersely oblong-ovate; umbonal region neal'ly cen- tral, pro\'idcd with a single, ohlong, accessoria~ valve, 1~·hic~1 is truncate al one end, and reaches to the anterior tenmnat1on, where thc \'alves meet; the gape or opening ncarly cil'cular; from the umbones a deep fu1Tow emanales, and tcrminatcs 011 the base ; anterior half of the valvcs considerably longcr than lhe other, bcinn- abruptly lengthened from the mesial furrow; the superior sitle abruptly descending, terminating in a ~lunt beak the lower sicle of which is acutely hollowed, procluc111g a stro;gly areuatecl basal line, in this half ~f the ".alves, which is covered with close-set, oblique, undulat111g stnrc; these are lying nearly parallcl 011 the other half of t~1e valves, ancl gra~ dually become obsolete towarcls the supenor cdge of them, thi 5 sicle is roundccl, ancl ncarly closecl; inside white, smool~, ·ti ¡ roun-h wrinkled tubercle, situate 011 the marg1n w1 1 a arge, º , . ¡ above the teeth, anti a longitudinal rib, correspond111g to t ie externa! groove. d. · · ¡ ¡ · The longitudinal externa! furrow will at once ist111gu1s l tus from P. parva. . Found at Torb_ay, but is a rarc species. S cction I 1.-f/alvcs clestitutc of a lo11gitmlinaljwTow. Found on mauy of the Dritish an<l Irish coasts, burrowing in harcl clay, mal'!, ami thc stumps of old trces. This specics is sometimes found two inchcs in length, ali(( seven in breaclth. 7. PnoLAS CANDIDA, pi. XLVIII, f. 6, 7, 8, 9, 10. Phf!las call/licla, First Ecl., pi. !), f. 6, 7, S, 9, 10; Pholas cc111cliclus, Pennant, IV, p. 76; Montagu, p. 2·1; Dono\'an, IV, pi. 132; Fleming, p. ,157; Turton, Ifo·., p. 10. Shell thin, fragile, semipellucicl, transversely clongatecl, ami white, slightly inc\ining to yellow, but snow-whit e in other spe- cimens; both sidcs roull(lecl at thcir cxlrcmities; umbonal region co,·ered by an elongated, acccssory plate, rounded nt the posterior side, all(\ acule at the other exlremity, with a hollow groove in ils centre, and obliquely sll'iated on both sidcs; mnbones placed near the anterior side, which is very short ; thc othcr side long; surfacc coverc<l with wide-sct, longitu- dinal, all(I transverse striro, prickly al the anterior side; hinge reílected, and provicled with a small, trans\'ersc, slightly bent denticle in one valve ; iusidc smooth, glossy, whitc, with a slcnder, arcuated, tooth-\ike process in both valves, unclcr thc umbone5. Inhabits limestone rocks all(I hard clay, 011 coasts of Dritain ali(! Ireland. 8. PnoLAS l'ARVA, pi. XLVIII, f. 11, 12. many of thc Pliolas ¡uwva, First Ed., pi. !), f. 11, 12; Pliolas ¡,m·vus, Pennant, IV, p. 77, pi. ,10, f. 13; l\fontagu, p. 22, pi. 1, f. 7, 8; Turton, Biv,, p. 9; Fleming, p. 457, Shell rathcr slrong, transversely oblong-ovate; rough, ami pale yellowish-brown exlernally; anterior sicle narrowed into a produced, somcwhat curl"ed beak, its superior marg'.n reílexed, and very open at the extremity; umboncs not qmle central, and covered by an elongated, spear-shaped, ac~cssory process, which is rounde<l at the posterior si<le, an<l shghtly hollowed in the centre, with arrow-shape<l strioo; margin of the umbo provicled with a round, smooth tubercle; externa! s_urfacc, nl the anterior side, longitudinally and transversely stn~te<l, but smooth on the oppositc extremity; inside smooth, wlnt_e. This is a i·ery local species, but is found plenllfully nt Torbay. [ found one specimen on the bcach at St. Cyrus, Kincardinshire. 9. PH0LAS STRIATA, pi. XLIX, f. 5, 8. Pholas striata, First Ed., pi. 8, f. 5, 8; Montagu, P• _26; D I\ r pi 117 • Turton, Biv., p. 11; Pholas con01des, onovan, , • , G. PnoLAs DAC'f:'Los, pi. XLI;,/';::~ 3Pcnnant, IV, P· Pholas clact1 1 fos, Í'll"Sl Ed., pi. 8 • · ' D IV \ Fleming, P· 457, . . Shcll trans\'ersely conoid; the antcnor s1de broa<l, very open, covered by two shicld-shaped, accessory platcs, and strongly .,1 20 ncl 558' OllOl':111, > p ' 76, pi. 3!), f. 1O; Ivlontagu, P· . ª r. ' 'I' 13· 8. Flcmnw, P· 4.i7, 118; urton, 1 "·, P· ' 0 1 bonal rcrrion placed Shell greatly elongated transverse _yl; um ·es of :Cns on the .d ílexed w1l l a sen considerably to onc si e, re · centrically slriatcd . 1 d . ed with two con externa! s1( e, an covcr . 1 . ll • 011 the posterior . ted long1tu( ma y, valves, wh1ch are connec 1 . 1 1 . t d stri:c separatcd from the smooth part arcuate(, w1t I ce una e , , k • . 1 d ¡· e and tcrminatinrr in a sharp bea ; the by a famt <epresse 111 , 0 • ·c1 · ¡ rly striated transverscly; umbones placed P osterior s1 e 1rregu a ·d and covere<l by n large, heart-shaped, much to one s1 e, . . h . , process • by the s1de of wluc 1s a narrow, smooth, accessor) '