S90 MOLLUSCA. PERNAD^. Gryph^a. 



3. G. dilatala — 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, -ttdth 

 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 oXA.— Sower. 

 Min. Conch, t. ccclxviii Middle Ooolite. 



6. Gr. 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. co/M»raia.— Ovate, rounded, expanded posteriorly, smooth ; beak at- 

 tenuated, incurved, oblique — Sower. Min. Conch, t- ccclxxxiii. £ 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. ^.—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.— C/wcfer Oolite. 



10. G. MaccwWocAiJ.— 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. 



1 1 . G. minuta Orbicular, gibbose ; beak spiral : lobe obscure.— iSower. 



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



PERNAD^. 



Gen. PERNA. — Shell siibequivalve, oblique ; hinge with nu- 

 merous transverse parallel teeth, receiving the hgament in 

 the interstices ; a sinus at the beak for the passage of the 

 byssus. 



1 . P. quadrata. — Quadidlateral, one side shorter than the other three ; 

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

 tuse carinjB ; beaks prominent. — S'otoer. 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 disjiosed Sower. Min. Conch, t. dx. f. 1-4 — In Green Sand. 



