MONOMYARIA. 127 



Genus U.—GRYFUMA.— Lamarck. 



Generic Character. — Shell inequivalve, free ; lower valve 

 large and concave, with the beak large, projecting, and spi- 

 rally curved or involute; upper valve small, flat, and resem- 

 bling a lid ; hinge without teeth ; the cardinal hollows 

 oblong, arcuated; a single muscular impression. Animal 

 unknown. 



Tliis genus is distinguished fi-om Ostrea by the very deep and 

 crenated lower valve, and by its summit being terminated by a long 

 spirally incurved beak, slightly tiu-ned to one side ; and the edge sharp 

 and angular. 



GryphcBa angulata. — The Angulated Gryph^a. Plate 

 XV. fig. 1. Oblong-ovate, with three longitudinal, cari- 

 nated ribs below; beak large, somewhat oblique. Four 

 inches long. Habitation unkno\vn. A specimen of this 

 rare shell is in the Museum of the Jardin du Roi, at Paris. 



TRIBE II. PECTIXIDES. 



Shell for the most part regular, compact, and not foli- 

 aceous ; the ligament either internal, or partly so. 



Genus 15.— PODOPSIS.— Xaraarc^. 



Generic Character — Shell inequivalve, nearly regular, 

 adhering by its lower beak; without ears; the lower valve 

 larger, more convex, and produced at the base ; hinge with- 

 out teeth; ligament internal. Found only in a fossil state. 

 They nearly approximate the genus Gryphsea, from which 

 they are distinguished by the summit of the lower valve not 

 being recurved, though much advanced beyond the upper 

 valve. 



Genus 16.— SPONDYLUS — Linnceus. 



Generic Character. — Shell inequivalve, adherent, cared, 

 spined, and rough, with unequal beaks; lower valve with 



