154 PROCEEDINGS OF THE ACADEMY OF [1883. 



adapted for crushing hard substances. The food of such species 

 was probably mollusca. There were but few herbivorous forms, 

 and these {Diastichus sp.) not typical, but related to the adjacent 

 carnivorous genera. Especial interest attaches to the present 

 distribution of some of the genera. Diastichus is the only one 

 which is extinct, so far as known, though its characters approach 

 those of existing genera so nearly, that it may be found at any 

 time in the recent fauna. Mylocyprinus has a living species in 

 China. Leucus is found in Europe and Asia. Myloleucus is 

 American, and is confined to the lakes of the Great Basin and 

 California ; two species occurring in Utah and two in Oregon. 

 Cliola is found in North America east of the Sierra Nevada. 

 Squalius is generally North American and European. 



MYLOCYPRINUS, Leidy. 



Proceedings Academy Phila., 1870, 70. Cope, Proceeds. Amer. Philos. Society, 1870, 

 543. Mi/lophari/nf/odon Peters, Monatsberichte Berlin Academy, 1880, 925. 



I am acquainted with three species of this genus ; two extinct 

 from Idaho, and one, the Mylocyprinus sethiops Basilewsky, 

 {Mylopharyngodon Peters) recent, in China. The pharyngeal 

 bones of these species may be distinguished as follows. I know 

 those of the M. sethiops from a figure given by Prof. Peters. 



I. Teeth commenciug near the symphysis ; curvature of pha- 

 ryngeal very abrupt ; apex shorter than tooth-row ; 



31. inflexus. 



II. Teeth commencing at a distance from symphysis, leaving a 



style; curvatui-e gradual. 



Style and apex each shorter than tooth-row ; M. robustus. 



Style and apex each longer than tooth-row ; M. sethiops. 



Mylocyprinus inflexus Cope, sp. nov. 



Established on two pharyngeal bones of the left side, one of 

 which indicates a fish of perhaps two pounds weight, and the other 

 one of half the size. Its form is peculiar in the very abrupt curve 

 of the external border, the. great abbreviation of the style, and 

 the shortness of the tooth series. The proximal and distal ex- 

 tremities of the bone are connected across the concavity byja thin 

 expansion of the inner border, not seen in M. I'obustus. The first 

 tooth is small, but larger than the corresponding one sometimes 

 seen in 31. robustus, so that I would be incliued to think it a per- 

 manent character, were it not wanting from the smaller specimen. 



