TRANSACTIONS OF WAGNER 

 672 



TERTIARY FAUNA OF FLORIDA 



two oysters bred of the same parent in different subgenera, according to 

 their growth in quiet water on a pebble, or in running water on a twig. 



Subgenus Loplia Bolten, 1798 (Rastellum [Llhwyd, 1699] Fischer, 1886; 

 Alcctryonia Fischer de Waldheim, 1807; Dcndostrca Swainson, 1840). Valves 

 similarly sculptured, sharply radially plicated, with their margins similarly 

 crenulated, without alae; their apices not spiral, the shell frequently arcuate. 

 Type Ostrea crista-galli Linne. Eocene to recent. 



Subgenus Ostreola Monterosato, 1884. Valves with small, close radial 

 riblets, less conspicuous on the upper valve, but ending on the margins with 

 small crenuhe, otherwise as in Crassostrea. Type Ostrea stcntina Pay- 

 reaudeau ; ex. 0. cqiicstris Say. Eocene to recent. 



Subgenus Gryph&osirea Conrad, 1865. Valves discrepant, the lower 

 valve smooth or concentrically striate, larger, with incurved apex; hinge-line 

 with a posterior and sometimes an anterior wing ; upper valve with distant 

 elevated concentric laminae, flatfish or concave, with short apex ; the margins 

 of the valves entire. Type Ostrea subcvcrsa Conrad = 0. cvcrsa (Mellv. ?) 

 Conrad, + ? 0. vomer Morton. Eocene. 



As we recede in time the lines of demarcation between these groups 

 gradually fade, and yet, even in the Cretaceous, species are found which 

 illustrate them. The oldest type is that of Crassostrca. The group called 

 Grypltcea is connected by slow gradations with Ostrea, but of the species 

 which best illustrate GrypJuca none is known from Tertiary or recent faunas. 

 Exogyra is a clearly distinct genus when confined to species with the typical 

 characters. The subgenus GrypJiceostrea Conrad was founded on an Eocene 

 shell closely resembling a French Eocene species (cf. Smithsonian Checklist 

 Inv. Fos. ; Eocene, by T. A. Conrad, p. 33, 1866) and hardly distinct from 

 the Cretaceous Ostrea vomer Morton. 



Subgenus GRYPH^A Lamarck. 



Gryphaa Lam., Syst., An. s. Vert., p. 398, 1801, ex pnrtc. 



Gryphaa Bosc, Hist. Nat. Coq., ii., p. 307, pi. 15, fig. I, 1802 ; Roissy, Hist. Nat. Moll., 



vi., p. 202, 1805 ; Cuvier, Regne An., ii., p. 459 ; Woodward, Man., p. 255, 1851. 

 Gryphaa. (sp.) Lam., Hist. An. s. Vert., vi., p. 197, 1819 ; Fischer, Man. de Conchyl., p. 



927, 1886. 



Gryphaa A. Blainville, Man. de Mai., p. 522, 1825. 



Pycnodonta F. de Waldh., Bull. Mosc., viii., 1835. (G. vcsicularis Lam.) 

 Type Gryphcca arena/a Lam., Enc. Meth., pi. 189, figs. I, 2; not Gryphaa Sacco, 



Moll. Terz. Piem., xxiii., p. 21, 1897. 



