142 CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY III. 



can fromis Laheo of Cuvier and Valenciennes. Its essential cbaracter — 

 the absence of tbe lateral line — was first noticed bj J^rofessor Agassiz, 

 who identified its typical species with Catostovius {Moxostoma) anisiirus 

 llaliiu'sque, and therefore erroneously called the genus Moxostoma. 

 The application of the name Moxostoma to the lied Ilorse group was 

 pointed out by the present writer in 187G ; the name Erimyzon being 

 then suggested for the group now under consideration. 



The use of the name TereUdiis for this genus has been lately sug- 

 gested by Professor Cope, its species being among those enumerated by 

 Kafinesque as composing his " omnium gatherum " to which the name 

 Tereiuhis was applied. If we subtract from the original group Tcrctulus, 

 the dillerent coujponent genera in order of time of proposal, the last 

 one lett would be Erimyzon, or rather Minytrema. But the name Tere- 

 iulm has already been restricted hy Professor Cope to the Red Horse 

 group, the principal component of Kafinesque's Teretuius. In my opin- 

 ion, it should remain there, although the earlier name Myxostoma renders 

 it but a synonym. Wo cannot afford to reconsider our use of these old 

 collective generic names whenever a new genus is proposed. The "rule 

 of exclusiou", if stiffly adhered to, would require the substitution of 

 Acomus for Paiitostcus, inasmuch as a species of the latter genus was 

 referred by Girard to the former. This question is further discussed 



under Myxostoma. 



Generic Characterizations. 



Labeo DeKay, 1842. — "Dorsal ^ofg. No spines nor barbels. Lips llesb}*, and fre- 

 quently crenated." — (DeKay, Xeic York Fauna, Fishes, 192.) 



Moxostoma Agassiz, 1855. — "Tbe species of tbis genus contrast greatly witb those 

 of all otber genera of tbo family of Cyprinoids, by tbo total absence of external open- 

 ings in tbo lateral line, visible upon tbe scales. Tbcre-is indeed no row of iKrforatid 

 scales upon the sides of the hodif, to mark tbo main course of tbo system of tubes per- 

 vading tbo skin in most fishes, and tbe pores traversing tbe skin which covers the 

 skull and cheeks, as well as tbo lower jaW, are so minute as to escape tbe unarmed eye. 

 In tbis respect tbo genus Moxostoma dillVrs greatly from all otber abdominal fishes in 

 which the lateral line is distinctly marked by a series of tubes traversing a prominent 

 row of scales along tbe sides, and extending through the mastoids to the forehead, 

 and along tbe preopercle to tbe symphysis of the lower jaw. Tbis total absence of a 

 lateral line is compensated by tbe presence of a few deeper radiating furrows in tbo 

 posterior field of all tbo scales. 



•' Tbe longitudinal diameter of tbe scales exceeds greatly the transverse, but the 

 scales are imbrioute«l in such a manner that tbe portion visible externally aj)pears 

 higher than long. Tbe c«'ntre of radiation is pbn-cil in tbi- middle of tbe scales; there 

 are no radiating furrows jipon tbe lattral fields, those of tbe posterior fuld are fewer 

 and deeper thau those of tbo anterior field ; tbo concentric ornamental ridges of the 



