104 



MOLLUSCA. 



[CORBULACEA. 



liinge with an obscure, conic tooth in one valve, and a cavity 

 for its reception in the other, with an obscure, nearly obsolete 

 tooth on each side of it. 



This is so nearly allied to H. minuta, that we should have 

 considered it a mere variety, but the total want of spines inclines 

 us to think that it may be distinct. The figure we have given 

 is from a specimen recently taken alive at Dunbar; Turton 

 gives as its locality Torbay and Dublin Bay. 



Genus 28 Sphenia — Turton. 



Shell transverse, incquivalve, inequilateral, general form flat- 

 tish wedge-shaped, gaping at the anterior end; hinge of the left 

 valve with an elevated, transversely dilated tooth, that of the 

 right valve with a concave tooth, and small denticle behind it; 

 destitute of lateral teeth ; two small muscular impressions in 

 each valve; pallial impression with a large tongue-shaped sinus, 

 emanating from the anterior side, and reaching nearly the mid- 

 dle of the valves ; ligament external. 



1. Sphenia Binghami, pi. XLII, f. 17, 18, and 22. 

 Sphenia Binghami, First Ed., pi. 14, f. 16, 17, 18; Turton, 



Biv., p. 36, pi. 3, f. 4, 5, and pi. 19, f. 3 ; Fleming, p. 465. 



Shell transversely oblong-ovate, subcompressed, wedge-shaped, 

 truncated at the hinge, with the superior margin frequently a 

 little contracted about the middle, gradually tapering towards 

 the anterior end, which is slightly gaping, and subtruncate; urn- 

 bones rather prominent, with their beaks not quite opposite, but 

 divaricating from each other ; whole surface covered with a 

 brown, wrinkled epidermis, which extends beyond the anterior 

 side; inside glossy, white, with a purplish tint; the margin plain, 

 and sharp ; the elevated tooth gradually diminishing, and ex- 

 tending nearly half way along the hinge line. Length a quarter 

 of an inch ; breadth half an inch. 



Found among the rocks at Torbay, by Dr. Turton and Gen. 

 Bingham, after whom it was named by the doctor. 



2. Sphenia Swainsoni, pi. XLII, f. 16, 23, 24. 

 Sphenia Swainsoni, Turton, Biv., p. 37, pi. 3, f. 3, and pi. 



19, f. 2. 



Shell transversely oblong-oval, wedge-shaped; the anterior 

 side round; umbones nearly central; a concave tooth, lying hori- 

 zontally, and pointing inwards. Length a quarter of an inch ; 

 breadth about half an inch. 



This species is somewhat more oval in its form than the S. 

 Binghami. 



Found among the rocks at Torbay. 



3. Sphenia decussata, pi. XLV, f. 3. 



Mya decussata, First Ed., pi. 10, f. 3; Montagu, Sup., p. 20, 

 pi. 28, f. 1; Fleming, p. 463; Sphenia decussata, Turton, Biv., 

 p. 38. 



Shell suborbicular, slightly inflated ; umbones obtuse, re- 

 curved, and situate nearest the posterior side; colour yellowish- 

 white, crossed by rather remote, concentric, ridges, which are 

 decussated by strong, regular, longitudinal stria 1 , forming tuber- 

 cles at the anterior end; inside smooth, white; in one valve a 

 broad, erect tooth ; in the other a projecting lamina, with a 

 small pit for the reception of the tooth in the opposite valve. 

 Length not quite half an inch ; breadth somewhat more. 



Found in the Frith of Forth, by Captain Laskey. 



Family VI. — Corbulacea. 



Shell incquivalve, and for the most part one valve somewhat 

 larger than the other ; ligament placed interiorly. 



Genus 29 Pandora Bruguiere. 



Shell free, thin, internally pearlaceous, inequivalve, trans- 

 verse, inequilateral ; the anterior side the longer, subrostrated, 

 and slightly gaping at its extremity ; one valve flat, with two 

 internal, anterior ribs, and with its anterior margin turned 

 downwards, provided with a single, oblong, obtuse, cardinal or 

 hinge tooth, situate behind the ligament ; the opposite valve 

 concave, and destitute of teeth, but furnished with an indistinct 

 cicatrice, on which the tooth of the flat valve rests, when the 

 shell is closed ; in each valve are two distant, lateral, muscular 

 impressions; ligament internal, its sides lodged in, and attached 

 to an elongated cicatrice, which lies inclined to the anterior side 

 of the valves; in some species the cicatrix is produced into an 

 elongated, divergent lamina, stretching from the umbo towards 

 the anterior side of the shell, and terminating near the inner 

 side of the anterior muscular impression. 



1. Pandora rostrata, pi. XLVII, f. 5, 12, 13. 



Trutina solenoides, First Ed., pi. 13, f. 5 ; Pandora marga- 

 ■ritacea, Turton, Biv., p. 40, pi. 3, f. 11, 12, 13, 14; Pandora 

 incequivalvis, Fleming, p. 466; Solen pinna, Montagu, p. 566 ; 

 Tellina inequivalvis, Montagu, p. 71 ; lb., Sup., p. 27; Dono- 

 van, II, pi. 41, f. 1 ; Maton and Rackett, p. 50. 



Shell transversely oblong and subovate, thin, and brittle; one 

 valve nearly flat, the other moderately convex ; the hinge line 

 of both valves arcuated ; umbones placed much to one side ; 

 posterior side extending into a lengthened, obtusely subtrun- 

 cated beak ; the other side short, and rounded ; surface cream- 

 white, with a pearly gloss, smooth in some specimens, but 

 transversely wrinkled in others ; two teeth in both valves, but 

 destitute of lateral ones; inside white, and slightly nacred; each 

 valve provided with a blunt tooth, running parallel from the 

 umbo, that in the convex valve largest, and with an uneven 

 surface, these not inserted, but stand by the side of each other, 

 when the valves are closed. Length nearly half an inch ; 

 breadth one inch ; but sometimes considerably more. 



This species inhabits the sea at Dawlish, Guernsey ; and in 

 several places on the Irish coast. 



Genus 30. — Corbula. — Bruguiere. 



Shell incquivalve, one valve being generally small and flat- 

 tened, the other large and convex; subequilateral, transverse, 

 generally gibbose and close ; each valve usually furnished with 

 a single, conical, recurved, ascending, pointed tooth, at the side 

 of which is a small concave depression, — very deep in some 

 species, which serves either for the reception of the ligament, 

 or the tooth of the opposite valve ; two distant, lateral, some- 

 what irregular, muscular impressions in each valve ; pallial 

 impression posteriorly angulated, with a very small sinus ; 

 ligament internal, fixed to the tooth of the lesser valve, and 

 inserted in the depression by the side of the tooth, in the 

 larger valve. 



