288 FOSSIL OSTREIDiE OF NORTH AMERICA. 



as well as marine waters. In closing these remarks it is proper to call 

 attention to tbe modern aspect of the oysters of the great Laramie sea, 

 as illustrated on Plates LVIII to LXI. 



In the following treatment of the subject of this memoir I shall follow 

 essentially the same plan that was adopted for the Review of the Non- 

 Marine Fossil Mollusca in the Report of the Director for last year. A 

 rectification of all the errors that have been made by different authors 

 in their former publication of the species herein enumerated, is not at- 

 tempted, but a part at least of the most obvious errors will be discussed 

 or mentioned. Under the head of each geological period in which any 

 of the Ostreidse are known to have existed, and under the sub-head- 

 ings respectively of the three recognized genera, all the species that 

 have been proposed by different authors will be given in alphabetical 

 order. The synonymy, at least in part, of each proposed species will 

 be given in connection with its entry. 



CARBONIFEROUS. 



It has already been shown to be a well recognized fact that the oyster 

 began its existence early in the Carboniferous age, and that the species 

 had at that early period the distinguishing characteristics of true Ostrea. 

 It is somewhat remarkable, however, that while the fossil species of the 

 later periods are, as a rule, represented by great numbers of discovered 

 individuals, a sufQcient number of examples of the three published 

 species of Carboniferous oysters have not been discovered to give a 

 satisfactory idea of all their respective specific characteristics. It is 

 practically certain that throughout the Carboniferous age the oyster 

 held a precarious existence, and that it was nowhere and at no time 

 abundant until Mesozoic time. 



Our knowledge of the existence of the oyster in North America dur- 

 ing the Carboniferous age is based upon very slender evidence; only 

 one species having yet been recognized, and only one example of that 

 species having ever been discovered. 



Genus Osteea LinntBus. 



Ostrea patercula Winchell. 



(Plate XXXIV, Figs. 1,2.) 



The specimen upon which the description of this species was based 

 was obtained from the Kinderhook Group of the Lower Carboniferous 

 strata at Burlington, Iowa. The description, without illustration, was 

 published by Professor Winchell in the Proceedings of the Academy 

 of Natural Sciences of Philadelphia for 18G5, page 124. The figures of 

 the shell, which are given on Plate XXXIV, are copies of Professor 

 Winchell's unpublished drawings. 



