TRIBE LITHOPHAGI. 51 



wrinkles, always with two rather prominent blunt ridges on the 

 anterior slope. — Var. S. Pholadis. Tart. Biv. t. 2. /'. 11. 

 Oval rounded and somewhat open at both ends. \ . . 1 . — N. 

 Europe. — Hiatella Arctica closely resembles this species, but the 

 incurvation of its ligamental edge distinguishes it. 



S. Australis. Lam. 4. — Bl.t.80f.4. Ovate, turgid, transversely 

 striated ; anterior side subangulated by an oblique rib. — Var. Ob- 

 long, with varied transverse striae. S Venertformis. Lam. 

 5. — New Holland. 1 



S. Guerini. Desh. — Payr. t. I. f 6, 7, 8. Transversely 

 elongated, rather flattened, thin, transparent, yellowish-white, equi- 

 valve, inequilateral, posterior side the longer, rounded : hinge 

 with two teeth, palleal scar simple. — Mediterranean. 



S. Tenuis. Sow. Z. P. 1834. Oblong, thin, white under a 

 palish epidermis : posterior side short and subtruncated. 2 ^ 4 < — 

 Pacosmoyo. 



S. Carditoides. Con. Jour. A.N.S. Phil. 7. p. 255. t. 10. 



f. 8. Oblong oval, anterior side much longer, its extremity direct, 



ligamental margin straight and parallel with the ventral, white with 



minute radiating lines : cardinal teeth prominent. 1-J-. — California. 



S. Solida. Sow. Z. P. 1834. Oblong, solid, wrinkled, some- 

 what irregular, whitish under a corneous epidermis : posterior side 

 very short, anterior elongated, truncated, with two conspicuous 

 diverging ribs. f. . If. — C. America. 



S. Purpurascens. Sow. Z. P. 1834. Oblong, rather solid, 

 posteriorly very short, anteriorly truncated, epidermis very thin, 

 anteriorly purplish, J- . . 1 T ^. — W. Columbia. 



S. Californica. Con. Jour. A. N. S. Phil. 7. p. 256. t. 20. 

 f. 9. Ovate, elongated, white ; anterior side much longer, sub- 

 cuneiform, obtusely subtruncated; ventral edge incurved; posteriorly 

 obliquely rounded ; two distinct teeth in each valve. 1 . — 

 California. 



PETRICOLA. 



Subtrigonal, transverse, inequilateral; posterior side rounded, 

 and the anterior attenuated, and slightly gaping ; hinge with 

 two teeth in each valve, or in one valve only. 



P. Lamellata. Lam. 1. — E. 3. p. 746. — Payr. p. 34. Tri- 



1 Deshayes refers Corbtjla Australis, Lam. 1. to this 

 species, but as both the figure of Blainville and the description of 



Lamarck seem at variance with this hypothesis, I prefix the La- 



marckian characteristics .. ." Ovate, very inequilateral, slightly 



gaping at the sides ; the posterior side very short, the anterior 

 angular and more produced. (Bl. t. 78. f. 3.)" 



e 2 



