Cope.] ^'^'^ [Dec. 2, 



cliilus and Cyprinus ; tliougli it lias fewer teeth than either, its formula 

 4 — 4 or 2.4 — 4.2, being that of the majority of the existiwg American genera. 

 According to Agassiz, the first- named displays 2.2.5- — 5.2.3 etc. ; while in 

 the latter they are 1.1.3 — 8.1.1, and have concentrically sulcate grinding 

 surfaces. In the present genus, these surfaces are smooth, except where 

 excavated by use. The inner series is represented by two rudimental 

 teeth, which are often wanting. 



In describing the pharyngeal bones which belong to this genus, Leidy 

 commits the error of inverting them, calling the inferior extremity the 

 superior, etc. The symphyseal articulation of the bones he then regards 

 as designed for articulation with the cranium, a structure which, it is 

 needless to observe, has no existence in this division of fishes. 



Among the numerous specimens brought by Capt. King, I recognize at 

 least three species, as follows : — 



Myloctpkintjs KOBtrsTUS. Leidy. 



L. c. 



Teeth rapidly diminishing in size upwards, the last with crown from 

 one-fourth to one-sixth the area of that of the first, and standing on an 

 elevated base which projects upwards. Alar margin expanding very grad- 

 ually, its greatest expansion generally below opposite to the basis of tho 

 first tooth, and considerably contracted opposite to the last tooth. The 

 superior limb short, flat, abi-uptly incurved. 



Eleven specimens, of which six belong to the left side. They vary in 

 the outline of the basis of the teeth ; in most, it is quite straight, in others 

 curved ; and, as a consequence, in these the superior part does not form 

 such a prominent buttress as in the first. A large species. Greatest 

 length of longest bone, 0.046 M. 



No. 9792, Catharine's Creek, Idaho. 



A single right pharyngeal of large size may indicate another species. 

 The tooth series is curved, and the first tooth unusually small. The 

 principal peculiarity is seen in the superior limb, which is long, slender, 

 and transverse, with a median contraction, and less flattening than in the 

 other specimens. Locality the same. 



Myloctpkinxjs kingii. Cope. 



Sijec. nov. 



This is represented by a single right pharyngeal bone of large size, and 

 is distinguished by peculiarity in the character of its teeth. These, in- 

 stead of diminishing in size upwards, increase, so that the fourth tooth 

 is larger than the first, instead of one-fifth the size as in M. robustus. 

 The second and thii'd are intermediate in proportions. The crowns are 

 broad, transverse ovals. The proximal limb of the bone is short, and 

 gradually expands into the ala, whose greatest width is opposite the 

 second tooth. The superior limb is short, narrow, and incurved. A 

 trace of basis for a small tooth of an inner series. 



