2G2 



More recently, Professor J. S. Newberry sent to me a small collection of 

 fossils, among which were seven additional specimens of pharyngeal hones, 

 identical in appearance with the former, which were slated to have been 

 found at Castle Creek, Idaho. 



Later, Professor Cope described, in the Proceedings of the American 

 Philosophical Society, a number of species and genera of extinct cyprfnoid 

 fishes from Catharine's Creek, Idaho. Among these he indicates the same 

 species as that to which the above-mentioned pharyngeals have been 

 attributed, and which have been referred to a previously undescribed genus, 

 as follows : 



Family CyprinidcB. 



MYLOCYPRINUS. 



Mylocyprinus robustus. 



The specimens, consisting of detached pharyngeal bones with teeth, from 

 which the genus and species were originally described, were all imperfect. 

 Having attempted the description without a previous comparison with the 

 corresponding bones of a recent cyprinoid, I find I have been so careless as 

 to have described them in an inverted position. The specimens later received 

 are better preserved, and among them are five complete ones. All the 

 specimens together exhibit such a variety in size and detail as to lead one to 

 -suspect they may represent several different species, though I view them as 

 belonging to a single one, the differences being, as I suppose, mainly due to 

 a difference of age. Six specimens, from Professor Newberry's collection, 

 are represented, of the natural size, in Figs. 11 to 17, Plate XVII, all of them, 

 excepting Fig. 16, being views beneath with the back part directed upward. 

 Fig. 1G represents an inner view, exhibiting the masticatory surfaces of the 

 teeth. 



The principal row of teeth consisted of five, as may be seen by the organs 

 themselves and their remains in Figs. 11 to 14, inclusive. They are all of 

 the true masticatory type, and are directed inwardly, opposed to those of the 

 other side. The first and last of the series are the smallest, and the inter- 

 mediate ones are comparatively large. 



In the smallest specimens, and the youngest, as I suppose them to be, the 

 second tooth is the largest, and from this they successively decrease in size 



