90 



MOLLUSCA. 



[CONCHACEA. 



Shell strong, subtriangular, subcordiform, and moderately 

 convex; umbones much turned to the posterior side, acute, and 

 approximate, beneath them a large, oblong, deeply impressed, 

 longitudinally striated lunule ; whole surface covered with 

 numerous, prominent, rounded, transverse, narrow ribs, which 

 are reflected at their superior edges, with several inequidistant, 

 remote lines of growth, almost all of which are provided with 

 very fine, intermediate, concentric striae, which can only be dis- 

 tinctly seen by the aid of a lens; cartilage or posterior side with 

 a long, wide, hollow space, which is beset with numerous, fine, 

 sharp, obliquely longitudinal stria 1 ; external surface cream- 

 white, frequently with several longitudinal rays of chestnut- 

 colour, differing in degree of intensity in various individuals ; 

 most commonly, the central one very broad, and often mottled 

 or streaked with zigzag markings; in some specimens, however, 

 it is devoid of markings of any kind ; inside white ; margin 

 finely crenulated. Size varying from three-quarters of an inch 

 to an inch and a quarter. 



This species is met with on almost all the coasts of Britain 

 and Ireland. 



•J. Venus rugosa, pi. XXXVI, f. 14. 



Venus rugosa, First Ed., pi. 20, f. 14; Pennant, IV, p. 95, 

 pi. 56, f. 50 ; Ortygia rugosa, Leach, MSS., p. 8 ; Venus Gal- 

 Una, var., Montagu, Syn., p. 113; Donovan, II, pi. G8, left 

 hand figure ; Venus pallida, Turton, pi. 10, f. 5. 



Shell strong, subtriangular, and subcordiform ; umbones 

 rather prominent, with an elongated lunule under them, and a 

 hollow elongated space on the cartilage hinge-line, with fine, 

 obliquely longitudinal striae ; whole surface of a uniform red- 

 dish-brown, rarely cream-white, covered by sharp, elevated, in- 

 terrupted, lamelliform ribs, which make the shell feel rough to 

 the touch; the intervening spaces covered with nearly obsolete, 

 longitudinal stria;; inside white; margin rathar blunt, and finely 

 crenulated interiorly. Seldom exceeding an inch in length. 



This shell bears a strong affinity to V. Gallina, but differs in 

 the form of the ribs, in being provided with longitudinal striae, 

 and in the valves being considerably more inflated, in propor- 

 tion to their size. 



Found in the Friths of Forth and Clyde, and Dawlish. 



3. Venus sulcata, pi. XXXVI, f. 12. 



Ortygia sulcata, First Ed., pi. 20, f. 12; Ortygia Pri- 

 deauxiana, Leach, MSS., p. 8 ; Venus Gallina, Turton, Biv., 

 pi. 9, f- 2. 



Shell subtriangular, subcompressed, the dorsal side rather 

 pointed, moderately strong ; umbones produced, much turned 

 to one side, with an oblong, cordiform depression under them ; 

 of a pale cream-white, with frequently from two to four rays 

 of a deep chestnut-brown, interrupted by the ribs, and the 

 intervening spaces often mottled all over with the same colour ; 

 frequently destitute of radiations or markings ; whole surface 

 covered with many transverse, nearly equidistant, somewhat 

 remote, elivatcd ribs, and the intervening spaces smooth ; 

 inside white ; margin blunt, and finely crenulated. Length 

 seldom more than three-quarters of an inch. 



Found on the Devonshire coast ; and also in Lough Strang- 

 ford, Ireland. 



Distinguished from the two former species, by its remote ribs 

 and more triangular form, which it assumes in its earliest stages 

 of growth ; and it is much less ventricose than either. 



4. Venus costata, pi. XXXVI, f. 13. 

 Ortygia costata, First Ed., pi. 20, f. 13. 



Shell suborbicular, subcompressed ; umbones somewhat ob- 

 tuse, and subcentral ; whole surface of a pale reddish-brown, 

 and covered by remote, rather elevated, transverse, white ribs ; 

 inside white ; margin crenulated. 



Differs from any of the preceding species, in its more orbicu- 

 lar form, and in the character of the ribs. 



Found by me at Seaton, Northumberland. 



5. Venus laminosa, pi. XXXVII, f. 14, 15. 



Ortygia subcordata, First Ed., pi. 19, f. 14, 15; Montagu, 

 Sup., p. 38 ; Venus lamhwsa, Laskey, Wernerian Mem., I, p. 

 384, pi. 8, f. 16, 16. 



" Shell ovate, with numerous concentric laminal ridges, very 

 little reflected, and not quite regular nor equidistant, but so 

 thin as to be almost membranaceous; between the ridges, 

 about the umbonal region, where a natural decortication has 

 taken place, it is finely striated in the longitudinal direction, 

 which shews that younger specimens are more generally fur- 

 nished with such striae, but in the only large specimen we have 

 had an opportunity of examining, scarcely any such markings 

 were observed but where the old shell had been superficially 

 separated ; umbo pointed, much reclined to one side, beneath 

 which is a broad cordiform depression ; but neither this, nor 

 the cartilage slope differs in colour from the rest of the shell, 

 which is wholly of a dirty white; inside white; hinge furnished 

 with four teeth in each valve, but the outer one above the 

 cordiform depression in one valve is obsolete, or formed only 

 by a cavity for the reception of the corresponding tooth in the 

 opposite valve ; margin finely crenulated. Length somewhat 

 more than an inch ; breadth about an inch and a quarter." — 

 Montagu. 



Said to have been dredged off the Isle of May, Frith of 

 Forth, by Captain Laskey. 



6. Venus verrucosa, pi. XXXVI, f. 16.* 



Clausina verrucosa, First Ed., pi. 20, f. 16; Venus verrucosa, 

 Poli, II, p. XVIII, pi. 21, f. 18, 19; Donovan, II, pi. 46; Mon- 

 tagu, p. 112; Fleming, p. 446; Turton, Biv., p. 140; Venus 

 Erycina, Pennant, IV, p. 94, pi. 54, f. 48. 



Shell suborbicular, cordiform, strong, thick, convex, subtrun- 

 cated at the lower angle of the dorsal side ; umbones much 

 indexed anteriorly, sharp-pointed, and approximate, beneath 

 them a large, elongated, cordiform, deeply defined lunule, finely 

 striated longitudinally, with the seam twisted; whole surface 

 covered with strong, elevated, transverse, varicose, concentri- 

 cally striated ribs ; the warts being larger, and more elevated 

 on the posterior side ; all the intervening furrows with broad, 

 wide-set, longitudinal striae, giving the shell a very rugose 

 aspect ; cartilage slope of the left valve inflected ; a deep, elon- 

 gated, obliquely striated space extends from the umbones on 

 the cartilage slope, to the subtruncature of the valves ; colour 

 of a dirty white, or dull rusty-brown ; inside smooth, white, 

 with a flat, thickened, crenated margin. 



In the young condition, the ridges are more perfect than in 

 the adult, with the interstices finely crenulated. 



Found on the coasts of Cornwall, Devon, Dorset, Kent, and 

 Northumberland; as also Dublin Bay, Portmamock, Balbrig- 

 gin, and other localities, Ireland. 



