1856.] 165 



the basal tuberosities. The crown of the lower true molar tooth is nearly an 

 inch and a half antero-posteriorly and an inch transversely. 



Specimens in the collection made in Nebraska by Dr. Hayden, for the St. Louis 

 Academy of Sciences. 



6. Pal;eoch(erus probus, Leidy. 



A species indicated by a superior first true molar, and a fragment of the lower 

 jaw with the last pre-molar and the succeeding two true molars, all of which 

 have the same form as in Palmochccrus lypus. Diameter of the superior molar 6 

 lines ; antero-posterior diameter of the second lower true molar 7 lines ; do. of 

 the last pre-molar 6 lines. 



Specimens from the collection made in Nebraska by Dr. Hayden, for the St. 

 Louis Academy of Sciences. 



7. Manatus antiquus, Leidy. 



The species is predicated on fragments of ribs found in the miocene deposits 

 of N'ew Jersey and Virginia, and on a fragment of a rib and an isolated molar 

 tooth, discovered by Capt. Bowman, U. S. A., in the sands of Ashley river. South 

 Carolina. The tooth apparently corresponds to the sixth or seventh upper 

 molar of 31. laiirostris, Harlan, than which it is considerably larger. It has no 

 anterior basal ridge, but from both of the inner lobes of the crown the summits 

 are prolonged in a curved line to the middle of the outer lobes. The specimen 

 measures in both diameters 9^ lines. 



8. Hydroch(erus J]]sopi, Leidy. 



Oromys JEsojn, Leidy. Pr. A. N. S., vii, 241. 

 Portions of two molar teeth in the collection of Capt. Bowman, from Ashley 

 river, S. C, prove that a fragment of an incisor tooth from the same locality 

 and previously referred to Oromys ^sopi, really belongs to a species of Hydro- 

 chcerus, about as large as the H. capybara of South America. 



9. CoMPSOSAURUS PRiscus, Leidy. 



The name is proposed on the remains of a saurian, obtained from the coal 

 field of Chatham Co., N. C, consisting of four teeth, which have been submitted 

 to my inspection by Dr. F. A. Genth. The teeth vary in size, are compressed 

 conical, uearly as broad as long, slightly curved, with opposed trenchant, 

 denticulate edges, constricted at the base, andapparently have been inserted by a 

 compressed cylindrical fang. The teeth are solid ; the enamel is striated ; and 

 in the larger specimens the base is longitudinally ribbed. They resemble those 

 of the lacertian Pala'osaurus from the magnesiau conglomerate of England ; but 

 in the latter genus the teeth are hollow. 



Accompanying the teeth is the specimen of a coprolite, containing a few 

 visible ganoid fish scales. 



Researches upon the Cyprinoid Fishes inhahiting the fresh waters of the United States of 

 America, west of the Mississippi Valley, from specimens in the 3Iuseum of the 

 Smithsonian Institution. 



By Charles Girard, M. D. 



The fishes which are the subject of the present memoir, were collected at 

 different times and periods, by several naturalists and surgeons attached to the 

 various surveys undertaken within the five years past. 



And first of all, there is the survey of the United States and Mexican boundary, 

 from 1851 to 1855. John H. Clark, who accompanied Col. .J. D. Graham, in 1851, 

 collected extensively in the rivers and creeks of Texas and New Mexico. Under 

 Major W. H. Emory, now commissioner of the boundary line, numerous collec- 

 tions were made by Dr. C. B. Kennerly, in Texas, in the valley of the Rio Grande 

 and provinces of Chihuahua and Sonora. 



The survey of routes for a railroad to the Pacific was commenced in 1853, 



