NO. 2125. FISHES FROM THE GULF OF CALIFORNIA— SNYDER. 577 



The other recognized Colorado species has been considered synony- 

 mous with P. hardus and P. virescens, described by Cope.^ The types 

 of P. delphinus and P. hardus are lost, and the locality from which 

 these and P. virescens came is not known with certainty. The 

 descriptions of all are equally brief. The type of P. virescens (No. 

 16758, U.S.N.M.) remains. It is apparently of the same species as 

 others in the United States National Museum identified by late 

 investigators as P. delphinus. It measures 370 mm., being by far 

 the largest specimen of the genus which the writer has seen.^ There 

 is some reason to suspect that this is not synonymous with P. del- 

 phinus (Cope), for that authority distinguishes the latter by its short, 

 wide head and thick body. He also says that the scales are sub- 

 equal. The type of P. virescens is relatively slender and the scales 

 of the anterior dorsal surface are much smaller than the others, a fact 

 which Cope records. However, as no more important reason appears 

 for distinguishing between P. delphinus and P. virescens, they are 

 here regarded as synon3niious. The skuU of this species is relatively 

 thin and the fontanelle constantly remains open. 



Unless the present treatment of these nominal fonns is at fault 

 it is evident that there are but two species of Pantosteus {Pantosteus 

 and Notolepidomyzon) in the Colorado system. Both are easily dis- 

 tinguished from species of Catostomus by the structure of the lips, and 

 they differ markedly from each other in the size of the scales. When 

 the crania of both are compared, it is observed that the heavy, firm 

 skuU of N. clarlci, with its closely fitting frontals and parietals, con- 

 trasts strongly with the comparatively light, thin skull of P. del- 

 phinus, the sharp-edged frontals and parietals of which are separated 

 by an elongate and narrow fontanelle. 



With these Colorado forms in mmd it will be of interest to examine 

 similar catostomids of the Bonneville Basin, where three species have 

 been described, Catostomus generosus Girard, Minomus platyrhynchus 

 Cope, and Minomus jarrovii Cope,^ only one of which has been gen- 

 erally recognized. The co types of C. generosus and M. platyrhynchus 

 are preserved in the Museum. The former represents a species with 

 a short, robust body and a very thick skuU without fontanelle, hence 

 belongmg to Notolepidomyzon, while M. platyrhynchus is relatively 

 slender and has a thin skuU with an elongate, narrow fontanelle,* 



1 U, S. Geol. Surv. Wyoming, Fourth Ann. Rept. for 1870 (1871), p. 436, Minomus bardus. Wheeler's 

 Explor. West of the 100th Merid., vol. 5, 1875 (1876), p. 675, P. virescens. 



2 Numerous specimens of Pantosteus measurihg from 230 to 395 mm., the largest of which weighed IJ 

 pounds, were lately collected by the writer while engaged in a survey of the Bonneville system under 

 the direction of the United States Bureau of Fisheries. In these the fontanelle is present. 



3 Proc. Acad. Nat. Sci. PhUa., 1856, p. 174. Proc. Amer. Philos. Soc. PhOa., 1874, pp. 134, 135. 



* The fontanelle, covered or closed as usual with a tough membrane, must have escaped the attention 

 of Cope, as M. platyrhynchus is the first species mentioned and described under his diagnosis of the genus 

 Pantosteus, which he characterizes by "a complete union of the parietal bones which obliterates the fonta- 

 nelle so universal among the suckers." 



81022°— Proc.N.M. vol.49— 15 37 



