66 UNIVERSITY OF COLORADO STUDIES 



The variation of this species has been given considerable attention since several 

 species now placed in its synonymy have been described. Three of these nominal 

 species have been reported from Colorado, Rhinichthys dulcis (Girard), Rhinich- 

 thys maxillosus Cope and Rhinichthys transmontanus Cope, the first two from the 

 region east of the mountains and the third from the Rio Grande Valley. Table 

 IV gives the results of an examination of the Colorado specimens as to position of 

 the dorsal fin. 



In Girard's original description of R. dulcis he says of the dorsal fin:' "Its 

 anterior margin is nearer the extremity of the snout than to the insertion of the 

 caudal fin." Cope in describing R. maxillosus states that "from the base of the 

 caudal to the base of the front ray of the dorsal equal from latter point to opposite 

 the middle of the orbit. "-^ Later in writing of this same species from the Rio 

 Grande in Colorado under the name of Rhinichthys transmontanus he says:^ 

 "It differs from the more eastern species in having the dorsal fin equidistant between 

 the base of caudal and the end of the muzzle, and in having the longitudinal series 

 of scales below the lateral line more numerous (12 to 13), and equal to the number 

 of scales above." Disregarding the other points of these descriptions which have 

 seemed similar enough to warrant the placing of all of these species in the same 

 synonymy by several authors, these three species differ in the position of the dorsal 

 fin. As may be seen from Table IV, but one of the specimens examined can be 

 referred to R. dulcis as defined by Girard and seven to Cope's R. transmontanus. 

 The remaining one hundred and sixty-seven specimens are all clearly referable to 

 R. maxillosus Cope. There seems to be no relation between the variation of the 

 position of the fin and the locality from which the fish were collected, for but one 

 of the specimens from the Rio Grande is of the R. transmontanus type. The fol- 

 lowing table (V) shows that there is not the correlation between the number of 

 scale rows and the position of the dorsal fin that has been suggested by Cope. 

 In general the scales of the specimens from the Rio Grande are slightly smaller 

 although the two series of counts overlap. The other variations looked for were 

 those of the fin rays. Two specimens only were found irregular in number of 

 fin rays and these have been mentioned in Table IV discussing the position of 

 the dorsal fin. 



From the material at hand it seems that the three species R. dulcis (Girard), 

 R. maxillosus Cope and R. transmontanus Cope are synonymous since all three 

 types have been found in the Platte drainage and two in the Arkansas and Rio 

 Grande drainages, in which case the oldest name applies. It is quite possible 

 that the examination of a large series of specimens of this fish from the Sweetwater 

 in Nebraska, the type locality of R. dulcis, would show a preponderance of indi- 

 viduals with the base of the first ray of the dorsal nearer to the tip of the snout 

 than to the base of the caudal, in which case the name R. dulcis should be restricted 



' Proc. Acad. Nat. Sci. Pliila., p. 185, 1856. 



'Ibid., p. 278, 1864. > Amer. Nat., p. 441, i87g. 



