229 IviGNiTic Stage 37 



SBCTION II. PAI,BONTOI/OGY. 



OSTREA. 



Ostrea compressirostra, PI, i, 2, 3; and pi. 6, fig. i, (2?) 



Syn. O. conipressirostra Say, Jour. Acad. Nat. Sci. Phila., vol. 4, p. 132. 



pi. 8 fig. 2. 

 O. bellovacina Con., Proc. Nat. Inst., 1842, p. 172. 

 O. conipressirostra (Tuomey) Thornton, 2d Bien'l &c., p. 270, 1858. 

 O. bellovacina Con., non Lam., Con., Amer. Jour. Conch., vol. i, 



p. 15, 1865. 

 O. compressirostra Heilprin, 3d Ann' Rep't U. S. G. S., p. 309, pi. 



65, 1884. 

 O. compressirostra Aid., Bull, i, Geol. Surv. Ala., p. 57, 1886. 

 O. compressirosti'a L,angdon, Bull. Geol. Soc. Amer., vol. 2 p. 603, 



1890. 

 O. conipressirostra Har., Amer. Jour. Sci., 3d ser. vol. 47, p. 302, 



1894. 

 O. compressirostra Say, Bull. Amer. Paleont., vol. i, p. 308, pi. 27, 



fig. 2, 1846. 



Saf s origi7ial description. — (See Bull. Amer. Paleont., vol. i, 

 p. 308.) 



Plate I shows the original figure of the species. It represents 

 a very common though not a ^Yell developed phase of the species. 

 Plates 2 and 3 represent different views of an uncommonly well 

 developed and well preserved specimen. 



Say, Conrad, Heilprin and others have noted the strong resem- 

 blance which this species bears to O. bellovacina of the Old World. 

 To any American, collecfting at the type locality of the latter spe- 

 cies, near Beau vais (Butte de la Justice), the resemblance be- 

 tween the Ostrece, Crassatellcs Slc. , found there and those found in 

 the lower Lignitic beds of his own country, seems most striking. 

 But by comparing these representative species side by side certain 

 differences are sure to be brought out. The plication on the 

 outer surface of compressirostra is loose, uneven, and sometimes 

 not well defined, while in bellovacina it is comparatively sharp 

 and well defined. It is well represented in Deshayes' Description 

 des Coquilles Fossiles des Environs de Paris, pi. 48, fig's i, 2; 

 pi. 49, fig's I, 2; pi, 50, fig. 6. The muscular impression is reni- 

 form and not pyriform as in compressirostra; there is a lack of 

 anterior alation in the larger valve, and the dehiscence or marginal 

 flexture is lower down on the posterior margin. Searles V. 

 Wood, in his monograph of the Eocene mollusca &c. published 



