142 CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY III. 



can genus Laheo of Ouvier and Valenciennes. Its essential cbaracter — 

 the absence of the lateral line — was first noticed by Professor Agassiz, 

 who identified its typical species with Catostomus {Moxostoma) anisurus 

 Kafinesque, and therefore erroneously called the genus Moxostoma. 

 The application of the name Moxostoma to the Red Horse group was 

 pointed out by the present writer in 1870 ; the name Erimyzon being 

 then suggested for the group now under consideration. 



The use of the name Teretulus 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 

 Teretulus was applied. If we subtract from the original group Teretulus, 

 the different component genera in order of time of proposal, the last 

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

 tulus has already been restricted by Professor Cope to the Red Horse 

 group, the principal component of Rafinesque's Teretulus. In my opin- 

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

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

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

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

 Acomus for Pantosteus, 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 long. No spines nor barbels. Lips fleshy, and fre- 

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



Moxostoma Agassiz, 1855. — " The species of this genus contrast greatly with those 

 of all other genera of the family of Cyprinoids, by the total absence of external open- 

 ings in the lateral line, visible upon the scales. There is indeed no row of perforated 

 scales vpon the sides of the iody, to mark the main course of the system of tubes per- 

 vading the skin in most fishes, and the pores travereing the skiu which covers the 

 skull and cheeks, as well as the lower jaw, are so minute as to escape the unarmed eye. 

 In this respect the genus Moxostoma differs greatly from all other abdominal fishes in 

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

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

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

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

 posterior field of ail the scales. 



" The longitudinal diameter of the scales exceeds greatly the transverse, but the 

 scales are imbricated in such a manner that the portion visible externally appears 

 higher than long. The centre of radiation is placed in the middle of the scales ; there 

 are no radiating furrows upon the lattral fields, those of the posterior field are fewer 

 and deeper than those of the anterior field ; the concentric ornamental ridges of the 



