wniTB.] CRETACEOUS. 295 



name of Ostrea cretacea, supposing it to have come from Cretaceous 

 strata in Alabama. It has since been ascertained that the strata from 

 •which his specimens were obtained are of Tertiary and not Cretaceous 

 age. This species has therefore been inchided in the list of the Tertiary 

 Ostreid® by Trofessor Heilpriu on a subsequent page. In the Second 

 Eeportof the Geological Survey of Arkansas, Plates VII and VIII, Dr. 

 Owen figured an oyster from Cretaceous roots of that State which he 

 referred to the Ostrea cretacea of Morton. Without knowing that they 

 came from different formations. Professor Coquand regarded them as 

 representing two distinct species. Therefore, in his Monographic du 

 Genre Ostrea, page 53, Plate XXIII, Figs. 8-10, he mentioned and fig- 

 ured Dr. Owen's form, and named it Ostrea frankllni. 



Ostrea denticulifera Conrad. 



This is another form the publication of which is very unsatisfactory. 

 It was described in the Journal of the Academy of Natural Sciences 

 of Philadelphia, Volume III (n. s.), page 321. On Plate 34 of that vol- 

 ume. Figs. 1 and 8 are given as illustrations of the species, but they are 

 not of such a character as to give much aid in specific identification. 

 Mr. Conrad's examples came from the Cretaceous strata of Mississippi. 



Ostrea diluviana Linnaeus. 



(Plate XL, Fig. 1 ; Plate XLI, Figs. 1, 2.) 



Some interesting specimens of this form were sent to the Smithsonian 

 Institution some years ago from the Cretaceous rocks of Bell County, 

 Texas. They seem to be specifically identical with the long-known 0. 

 diluviana of Linnaeus. At least they are so nearly like that European 

 species that I do not feel warranted in placing the Texan form under a 

 separate name. This shell has the toothed margin, and to some extent, 

 also, the characteristic marginal outline of Alectryonia, and it ought per- 

 haps to be ranged under that subgenus. 



Ostrea elegantula Newberry. 



(Plate XXXVI, Figs. 5, 6, 7.V 



Prof. J. S. Newberry, in his Geological Eeport which accompanies 

 that of Captain Macomb's Exploring Expedition, page 33, proposed the 

 name Ostrea elegantula for a small Cretaceous species which he found 

 abundantly in the valley of Canadian Eiver, but he gave neither de- 

 scription or figures of it. Professor Newberry has kindly furnished 

 for this article authentic specimens from his original collection, figures 

 of which are given on Plate XXXVI. This form is probably identical 

 with Ostrea hella Conrad, but as I am not quite certain of this, I give 

 both names a place in this list. Professor Newberry's reference to his 

 form was written before the publication of Conrad's description, but his 

 report was not published until long afterward, in 1876. 



