TRIBE LITHOPHAGI. 51 
wrinkles, always with two rather prominent blunt ridges on the 
anterior slope.—Var. S. Puotapis. TZurt. Biv. t. 2. f. 11. 
Oval rounded and somewhat open at both ends. 14..1.—WN. 
Europe.— Hiatella Arctica closely resembles this species, but the 
incurvation of its ligamental edge distinguishes it. 
S. Austrauis. Lam. 4.—BI1.t.80.f.4. Ovate, turgid, transversely 
striated ; anterior side subangulated by an oblique rib.k— Var. Ob- 
long, with varied transverse strie. S.VreNERIFoRMIS. Lam. 
5.—New Holland. 
S. Guerinit. Desh.—Payr. t. 1. 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. *~4.— 
Pacosmoyo. 
S. Carprtrorpes. Con. Jour. A.N.S. Phil. 7. p. 255. t. 10. 
J. 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. 14.—California. 
S. Sorrpa. 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. +#..12.—C. America. 
S. Purrurascens. Sow. Z. P. 1834. Oblong, rather solid, 
posteriorly very short, anteriorly truncated, epidermis very thin, 
anteriorly purplish. 2..1;4,.—W. Columbia. 
S. Cauirornica. Con. Jour. A. N.S. Phil. 7. p. 256. t. 20. 
J. 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. Lamevuata. Lam. 1.—L. 3. p. 746.—Payr. p. 34. Tri- 
1 Deshayes refers Corsputa Avstrauis, 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 
