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. sinuate- — 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, thick. — Sower. Min. Conch, t. ccclxxxiii. f. 3.— Middle 

 Oolite. 



9. G. giganleay— Orbicular, rather smooth ; upper valve thin, concave ; 

 lower valve convex, with a small, sharp, incurved beak ; hinge small.— Sower. 

 Min. Conch, t. cccxci — Under 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. Dxlvii. f. 1, 2, 3. — In Oolite. 



11. G. minuta Orbicular, gibbose; beak spiral: lobe obscure — Sower. 



Min. Conch, t. Dxlvii. f. 4 — In Oolite. 



PERNAD.E. 



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 . P. quadrate. — Quadrilateral, one side shorter than the other three ; 

 valves gibbose, unequal, the shorter side very concave, bounded by two ob- 

 tuse carinse ; beaks prominent Sower. Min. Conch, t. 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.solenoides Transversely much elongated, depressed, smooth; edges 



parallel; anterior extremity truncated, open ; teeth of the hinge numerous, 

 variously disposed Sower. Min. Conch, t. bx. f. 1-4 — In Green Sand, 



