GENUS BUBALICHTHYS. 203 



descriptions published by Professor Agassiz are almost worthless for the 

 distinction of species. It has accordingly seemed best to inc, as a tem- 

 porary arrangement, at least until more than tico species are shown to 

 occur in our waters, or until some one is able to show from examination 

 of Professor Agassiz's tyi)es what he really had in mind, to distribute 

 bis nominal species in the synonymy of the two which we know. I 

 have accordingly considered each of Agassiz's species and made it 

 identical with either the small-mouthed or the large-mouthed species, as 

 the description seemed to indicate. A third species, from Central 

 America, which I suppose belongs to this genus, is added from Dr. 



Giinther's description. 



Generic Characterizations. 



BuBALiCHTHYS Agassiz, 1855. — "At the time I viudicated the propriety of restoring 

 some of the genera established by Rafinesque among Cyprinoids, I did not suspect that 

 the genus Carjyiodes, as I then represented it, still contained two distinct types, though 

 I had noticed that some of the species had the anterior margin of their dorsal greatly 

 prolonged, whilst in others it hardly rises above the middle and posterior of that fin. 

 Having since examined the pharyngeals of all the species of this tribe which I havo 

 been able to secure from diiferent parts of the couutry, I find tUat those with a high 

 dorsal w^hich constitute the genus Carpiodes, have, in addition, very thin flat pharyn- . 

 geals with extremely minute teeth, whilst those with a low dorsal have triangular 

 pharyngeals with larger teeth, increasing gradually in size and thickness, from the 

 upper margin of the bones towards the symphysis. The difference in form of these 

 bones arises from the circumstance that the slight ridge upon tlie outer surface of the 

 arch in Carpiodes is transformed in this second type into a prominent edge, dividing 

 the outer surface of the arch into a posterior and anterior plane, meeting under au 

 acute angle. This structural homology is satisfactorily traced by the difference of the 

 external appearance of these two planes, the posterior one being full as the posterior 

 half of the flat outer surface of the arch in Carpiodes, whilst the anterior plane is 

 coarsely porous, indeed studded with deep pits analogous to the porous character of 

 the anterior half of the outer surface of that bone in Carpiodes. The teeth themselves 

 are compressed ; their grinding edge is rather blunt, slightly raised in the middle, and 

 provided with a little cusp along the inner margin, which is hardly detached from the 

 crown, and does not rise above its surface, as in Carpiodes, Ichthyohus and Cydeptus. 



" In this genus the bulk of the body is not placed so far forwards as in Carpiodes, the 

 greatest height being between head and tail. The upper outline of the body is less 

 strongly arched in advance of the dorsal ; the head is longer than high, and the snout 

 not more prominent than the mouth. The mouth opens obliquely downwards and 

 forwards, the lower jaw being nearly as long, as the upper. The lips are small and 

 granulated. The anterior rays of the dorsal are not separately prolonged beyond the 

 rest of the fin, though its anterior margin is higher than its middle and posterior por- 

 tion. The lower fins are as in Carpiodes. 



" The scales have many narrow radiating furrows upon the anterior field, none across 

 the lateral fields, and few upon the posterior fields, converging to the centre of radia- 



