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

82 MOLLUSCA. [NAYADES. ascen<ling rather nbruptly to,~arcls the posterior si~e, and form- ing 8 subrostratecl ter1'.1inat10~; ~mboncs promment, placed very near the anterior srde, wluch 1s short, ancl roundecl ; pos- terior siclc slightly gaping, much elongatccl, but not subrotund ami subangulatccl ; producccl by the somcwhat elevatcd ridge, which clivcrgcs from the umbones to the extreme point of the vah•e; cardinal tecth small, compressecl, minutcly scrrated; double, ami lamelliform, elongated in thc lcft valve, with a decp, pcrpenclicularly sulcatcd sinus in its sicle, for the recep- tion of the tooth of the right valre; the portion of the t oolh next the umbo somewhat acule; lateral tooth long and double in the lcft valve, single and sunk towards the umbo, nncl ncarly parnllcl; lateral tooth of thc right valve single, deprcssed towarcls the umbo, but asccnding, and more acule, as it diverges from thc umbo; insidc bluish-white, ancl iriclescent ; muscular impressions very deep; pallial impression well delinee!; outsidc of a clark olive-green, ami with rather deep, concentric wrinkles. Figs. 3 and 4, pi. XXXII, cxhibit the externa! and interna! appcarnncc of thc tccth. 'fhis spccies dilfcrs from U. pictontm, in its general length bcing more uniform, and in bcing broacler at thc posterior sido, aml lcss acule; in thc tccth bcing much smallcr, and lcss clcvatcd, as well os in the crcnulations 011 thcir uppcr siclo being less distinct, and lcss regular; in the shcll bcing much thickcr, ami its posterior side being con;iderably shortcr. Found in thc Wharf, ncar Ottlcy ; thc Aire, ncar Kcighlcy; 1hc \Yharf, near Dolton l3ridgc; ami thc Don, ncar Shcfiiclcl. 3. UNIO I\OS'l'RATA, pl. XXXII, f.!), 10, 11, 12. U11io rostmlll, Kokcil Muscum; Aldcr, Mag. Zoo!. and Ilot., II, p, 118; Lamarck, An. San. Vert., VI, pt. 1st, p. í7, No. 31 ; Unio clo11galala, Pfoiffcr, II, p. 35, pi. 8, f. 5, 6; Unio piclol'mn, vm·., Nilsson, I, p. 118, f f; lb., III, p. 23, f f; Ross- massler, VI, p. 55, pi. 2!), f. 409. Shell groatiy elongated transvcrsely ; umbones very ílat, placed ncar the nnterior siclo; hingc line but very lit tlc arcuatcd, ns far as thc cxtremity of the latcrnl teeth, from whencc it smldenly slopes both abore and bclow, termina- ting in a somcwhat rostmtcd form; basal line nearly parallel; primary teeth rnther thick, ami serrnted al thc cdge; lateral lecth long, aml consiclcrnbly elevated ; anterior muscular im- pression moderntcly sized, ancl <lceply sunk; below the nmbones, thcrc nrc inclicalions of remoto, nearly obsolete striro; intcrnal smf:ice of a bluish-whit e, with iridcsccnt reílec- tion~. Length nol n thircl of its breadth; thickness four-fiflhs of its leugth. 1-'igs. 11 ali(! 12, pi. XXXII, externa! and interna! represcn- tat ion of the tceth. This shcll tapers more abruptly in thinness towards the pos- terior siele, than any of its Ilritish congeners; nncl is considcr- ably more obt ll5c al its anterior sicle, than the U. pictoi'Wn; but its much more elongated form, will at once distinguish it from that shcll. I founcl this species in the canal, near Hull ; an<l \Villinm Thom¡;son, Esq., of l3elfast, procurecl it in the Avon, ncar Leamington. 4. UNlO TU)IIDUS, pi, XXXII, f. 5, 6, í, 8 . Unio tumiclus, Rctzius, Norn Testaceor. Genera, p, 1 í, No. 3; Unio tumida, Pfcilfer, II, p. 3-1, pi. í, f. 2, 3, ami pl. 8, f. 1, 2; Rossmassler, II, p. 117, pi. 3, f. 70 b; Ili., III, p, 27, pi. 3, f. 202, 203; Aldcr, Mag. Zoo!. nncl Ilot., II, p. 118; ill!fsca solida, T urton, Man,, P· 22, pl. 2, f. 13; lb., Conch. Dict,, p. 2,16, pi, 16, f. 2. Shcll vcry thick, solicl, cunciform, transversely oblong-ovatc, much inílated; umbones proclucccl, and placed very close, situatc ncar one cxtremity; anterior siclc short, 1·ounclcd; posterior sidc long, gradually sloping from thc umbones l>oth above ancl below, ancl terminating in a subtruncatecl bcak; cardinal tooth largc, single, thick, clevated, nnd finely serrat ed at the edgc, in the right valve, and double in the opposite ,•alve; muscular im- pressions small, ancl deeply sunk bolh before and behincl; pallial impression strongly dcfined; externa] surface with rather strong, concentric wrinkles, ancl lhe whole of a redclish-lirown, slightly tingcd with olivaccous-green; insidc white, with but little iri- descent lustre. Length half its brcaclth ; lhickness four-fifths of its length. Figs. 7 and S, pi. XXXII, externa! and interna! reprcscnta- tion of the teeth. Found in lhe Ncw Rivcr, near Lonclon; and the Avon, near Lcamington, Warwickshirc. 5. UNIO OVAL1S, pi. XXXI, f. 12, 13, 1'1. U11io ovalis, First Ed., pi. 26, f . 2; Leach, MSS., p. 1 O; 11/ya ovalis, Montagu, Test·. Dril., p. 563 ; /Jlya clc¡n·cssa, Donovan, Brit. Sh., III, pi. 101; JI/ya ovala, D onovan, Brit. Sh., IV, pi. 122, f. 1, 2, 3; /Jfysca ovala, Turton, Man., p. 21, pi. 2, f . 12; 11/ysca solida, Turton, Iliv., p, 246, pi. 16, f. 2 ; llnio t1t- midus, Rossmassler, I, pi. 1'1, f. 204; Un-io t·u111id11s, vm·., Ross- massler, VIII, p. 41, pi. 40, f. 542. Shell strong, thick, transvcrsely ovale; hinge lino arcuatecl; uml>ones prominent, wrinkled, and closely approximate; right valvc with a strong, doublc, erect, cardinal tooth, the higher portion situntc immccliately below the umbo, considerably elcvated abovc the margin, nncl two long, oblique, lateral lccth; muscular impressions of moderate size, thc anterior ones deep; pallial impression dceply clcfined; left valve with a single, erect, oblique, cardinal tooth, and a long, elc,·atcd, lateral tooth, which fits into the cleft betwccn thosc of thc oppositc valve; insicle iridcsccnt, and of a palo redclish-salmon colour, and the posterior sidc ~f thc vnlves often rough ami irregularly wrinkled; outside usually with strong, concentric lines of growth, which are often foliaccous al the posterior siclc, nnd of an olivaceous-brown colour ; thc umbones generally reclder, and frequently with longi tudinal racliations of palc ycllow, or bulf. Length upwards of three-fifths of ils breadth; thickness not two-fifths, Fig. 14, pi. XXXI, externa! representat ion of the teeth. This specics will be distinguished from thc t11mid11s, by its more oval form, ancl in the posterior sicle being less produccd, as well as by its tecth bcing thicker, the central portion of that in the right vall'e not so acutcly notched 011 its edgc, ami ratlier more elerntcd ; and thc shell is much lcss inílntcd. Found in the Ai re, near Skipton; the Ouse, nbo,·e York; the Severo, near Shrcwsbury; nt Kirkstal l3ridge, ncar Lcecls; ami in the canal, near Burnlcy. G. U:-10 DATAvus, pi. xxxr, r. 3, 3," 4, 5, G. U11io Batavus, First Ed., pi. 2G, f. 3; Lamnrck, An. San, Vcrl,, VI, pt. 1st, p. iS, No. 33; Nil,s011, p. 112, No. 8; Pfcif- fcr, I, P· 115, pi. 5, f. J ,1; Rossmassler, II, p. 20, pi. 8, f. 12S,