38 Bulletin 9 230 



by the Paleontographical Society, 1861, says, p. 18, regarding a 

 specimen brought from the New World by Charles Lyell : " I 

 have seen a specimen, in Sir Charles' cabinet, from Virginia, 

 (without a name), which, in some characfters resembles O. /z^/- 

 chra; I can scarcely think it stridlly identical either with it, or 

 with bellovachiay 



Heilprin has already called attention to the facft (3d Ann'l 

 Rep't U. S. Geol. Surv., p. 310) that the species from "Grove," 

 S. C, referred by Lyell to O. bellovacina ( Proc. Geol. Soc. 

 Ivond., Feb. 1845, P- 567) should probably have been referred to 

 O. carolinensis Con. We have already shown ( Bull. Amer. 

 Paleont., vol. i, p. 159, 1896) that certain specimens referred to 

 this species by lyangdon, are really another species, called first by 

 Gabb. , Q. crenulimarginata. Below we will show how others 

 from the upper Lignitic should be classed as a third species, O. 

 var. sylvceriipis . 



This species is extremely abundant and often of large dimen- 

 sions at Bell's Landing and Ft. Gaines. 



Localities (exclusive of Md. and Va. ). — Alabama: Nanafalia, 

 Tuscahoma, Yellow Bluff, Gregg's Landing, Bell's 

 Landing. Georgia : Ft Gaines, 



Ostrea trigonalis var. sylvaerupis, Pi's 4 and 5. PI. 6, figs. 3, a, 4. 



Syn. O. compressirostra Tuomey, ist Bien. Rep't, p. 146, 1850. 



O. carolinensis Con., Amer. Jour. Sci., vol. 40, p. 266, 1865. 



O. probably young of thirsce Gabb, Aid., Bull, i, Geol. Surv. 



Ala., 1886. 

 O. compressirostra Smith and Johnson, Bull. 43, U. S. Geol Surv. 

 p. 44, 1887. 



It is in deference to Ball's opinion that this form is referred 

 to as a variety of /rz'^^^w^/w Con., Proc. Acad. Nat. Sci. Phila., 

 1855, p. 259, and Wailes' Agr. and Geol. Miss., 1854, pi. 14, fig. 

 10. We have here but a half dozen rather imperfedl specimens 

 of trigonalis while at the National museum, the material from the 

 Jackson beds is far more satisfacftory. Our specimens of trigon- 

 alis are not so quadrangular nor so incrassated as sylvcerupis. 

 The more important features of the latter are as follows : 



Quadrangular or broadly oval in outline; valves very thick and 

 of a silicious granular texture: left valve very convex and heavy; 

 exterior sometimes marked by faint and irregular costations; in- 

 terior showing a moderately deep ligamental pit with small 



