ISo. 2. 



DESCRIPTION OF THE TERTIARY FOSSILS COLLECTED ON THE SURVEY. 



BY T. A. CONRAD. 



The California fossils, described from the collection of Dr. Newberry, consist of shells, which 

 appear to me to represent the Miocene period, or to have existed contemporaneously with the 

 fossil fauna of Virginia referred to that epoch. The few shells from Gatun, Isthmus of Darien, 

 are not sufficient to indicate precisely the geological age of that vicinity. The well known 

 univalve, Malea ringens, is one of the number, a shell which now exists only in the Pacific, and 

 I believe the genus is unknown in the Atlantic. The probability is, therefore, that posterior 

 to the Eocene period the Pacific was separated from the Caribbean sea by a narrower strip of land 

 than at present, and that while the land was rising towards the Pacific it was probably sinking 

 on the eastern coast. 



CALIFORNIA FOSSILS. 



UNIVALVE. 

 SCHIZOPTGA, Conrad. 



Bucciniform ; columella concave, plicate ; lower part of body volution deeply channelled, the 

 channel emarginating the columella. 



Schizopyga Californiana, Plate II, fig. 1. Volutions rounded, having revolving ribs and 

 longitudinal furrows, giving the ribs a nodulous character ; basal excavation profound. — Pro- 

 ceedings of Acad. Nat. Sc., Dec, 1856, p. 315. 



Locality. — Santa Clara, Cal. — Dr. Newberry. 



The above genus is probably related to Cancellaria. 



BIVALVES. 

 CllYITOMYA, Conrad. 



Cryptomya ovalis, PL II, fig. 2. Oval, compressed, posterior end truncated ; umbonal slope 

 angulated on the umbo ; beaks medial ; basal margin medially truncated ; disk medially 

 flattened. — Proceedings Acad. Nat. Sc. for Dec, 1856, p. 314. 



Locality. — Monterey county, Cal. — Dr. Newberry. 



Rather smaller than the recent C. cali/ornica, less regularly oval, inequilateral, &c. 



THEACIA, Leach. 



Thracia mactropsis, PI. II, fig. 3. Subtriangular, subequilateral, ventricose ; anterior side 

 cuneiform or subrostrated, posterior end regularly rounded ; ligament margin very oblique ; base 



