390 MOLLUSCA. PERNAD^. Gryph^a. 
3. G. dilatata — Orbicular, obscurely lobed ; upper valve flat, lower valve 
hemispherical — Sower. Min. Conch, t. cxlix. f. 1. var. ib. f. 2 In Oolite. 
4. G. sinuata — Suborbicular ; one side cuneiform ; beaks very small, late- 
rally incurved; one valve convex, subcarinated; the other nearly flat, with 
a sinus above the angle of the cuneiform side ; hinge-pit marginal^ long, nar- 
row, and curved — Sower. Min, Conch, t. cccxxxvi. — Iron Sand. 
5. G. bullata — Transversely obovate, irregular, smooth, thin, depressed, 
beaks small ; upper valve concave ; lateral lobe obscure, when old Sower. 
Min. Conch, t. ccclxviii.. — Middle Ooolite. 
6. G. vesiculosa. — Subrhomboidal, oblong, deep ; lesser valve concave, 
small, thin ; larger valve curved, composed of several distant coats. Sower. 
Min. Conch, t. ccclxix. — In Green Sand. 
7* G. columba — Ovate, rounded, expanded posteriorly, smooth ; beak at- 
tenuated, incurved, oblique — ,Sower. Min. Conch, t. ccclxxxiii. f. 1, 2. — In 
Green Sand. 
8. G. nana — Oblong, ovate, rugged, gibbose, beak oblique, incurved ; up- 
per valve pointed, Sower. Min. Conch, t, ccclxxxiii. f. 3 Middle 
Oolite. 
9. G. gigantea . — Orbicular, rather smooth ; upper valve thin, concave ; 
lower valve convex, with a small, sharp, incurved beak ; hinge small. — Sower. 
Min. Conch, t. cccxci.— Oolite. 
10. G. Maccullochii. — Obovate, oblique, gibbose ; beak produced, much in- 
curved; posterior lobe more or less distinct; the front rather angular. — 
Sower. Min. Conch, t. nxlvii. f. 1, 2, 3. — In Oolite. 
1 1 . G. minuta — Orbicular, gibbose ; beak spiral ; lobe obscure.*— 
Min. Conch, t. Dxlvii. f. 4. — In Oolite.. 
PERNAD^. 
Gen. PERNA, — Shell subequivalve, oblique ; hinge with nu- 
merous transverse parallel teeth, receiving the ligament in 
the interstices ; a sinus at the beak for the passage of the 
byssus. 
1. V. quadrata. — Quadrilateral, one side shorter than the other three; 
valves gibbose, unequal, the shorter side very concave, bounded by two ob- 
tuse carinse; beaks prominent. — Min. Conch. %. ccccxcii . — Under 
Oolite. 
Gen. GERVILLIA. — Shell inequivalve, inequilateral, beaks 
near the anterior extremity ; hinge long, with numerous 
pits and lamelliform teeth for the reception of the liga- 
ment. 
1. G. solenmdes . — Transversely much elongated, depressed, smootli; edges 
parallel ; anterior extremity truncated, open ; teeth of the hinge numerous, 
variously disposed.— *S'ow^r. Min. Conch, t. dx. f. 1-4..^ — In Green Sand. 
