INVERTEBRATE PALEONTOLOGY. 1<) 



Geuus GRYPKffiA, Lamarck. 



Synon. — Auricularia, AuricuHtes, &c. (sp.), of Lhwyd and some oilier pre-LinnaeaD authors. 



Gnjpkcm, Lain. (1801), Syst. An., 393.— Roissy (1835), Moll., 202.— Blainv. (1821), Diet. Sci. Nat., 



XIX. 533 ; and many other authors. 

 Grypliea, Eisso (1826), Hist., IV, 290. 



Ptjcnodonta, Fischer do Waldh. (1835), Bull. Mosc,., VIII, 118.— Courad (1860), Jour. Acad. Nat. 

 Sci. Philad., IV, 275. 

 Etym. — ypii}>, a griffin. 

 Examp. — GryphtBa arcuata, Lam. 



Shell generally more or less broad-subovate, usually free in the adult, 

 but often attached when young, very inequivalve, the lower valve being deep, 

 and in most cases having its beak produced and strongly curved upward, or 

 sometimes subspiral, and more or less oblique; upper valve nearly or quite 

 tlat, or sometimes concave, with its beak truncated ; ligament-cavity arching 

 with the beak in the lower valve, and merely occupying a slight impres- 

 sion in the nearly flat, transversely-striated, and truncated cardinal margin 

 of the upper valve ; surface generally with only concentric marks of growth; 

 muscular impressions as in Ostrea. 



The shells of this genus, especially in the well-developed adult, are gen- 

 erally readily distinguished from those of the genus Ostrea, by being less 

 irregular in form, with the beak of the lower valve more produced and 

 recurved. They seem also to be nearly always without the strong radiating 

 plications often seen in that genus and Exogyra. They likewise differ from 

 the latter genus in having the beak of the lower valve curved upward instead 

 of laterally. In young or undeveloped examples, however, it is sometimes 

 very difficult to distinguish Gryphcea and Ostrea ; a young Gryphcea being often 

 exactly like an oyster. In some cases, where the shell remained attached 

 during its whole growth to adult size, it has the umbo largely truncated, and 

 not showing the extended incurved character of the genus; but retained 

 much the form of a true ovster during life. 



The genus Qryphaia appears to be of more recent origin than Ostrea; the 

 oldest known examples being from the Trias. It is most extensively repre- 

 sented in the Jurassic rocks, occurs less abundantly in the Cretaceous, and is 

 rarely found in the Tertiary ; while only one species is known in the seas of 

 the present period, and that does not have the characteristic features of the 

 genus, as represented in Cretaceous and older rocks, very strongly marked. 



