NOTE ON DELTISTES, A NEW GENUS OF CATOSTO- 

 MOID FISHES. 



BY ALVIN SEALE. 



In studying the skulls of the different species of Chas- 

 mistes, a genus of Suckers characteristic of the land- 

 locked lakes of the Great Basins of Utah, Nevada, and 

 Oregon, I observed a notable difference in the form of 

 the gill -rakers of Chasmistes hixatiis Cope, as compared 

 with the other species. In this species the gill-rakers are 

 broad, shaped like the Greek letter [\ (delta), and their 

 edges are unarmed and entire. In the other species re- 

 ferred to Chasmistes, the gill-rakers are, as in Catostomus, 

 narrower and marked with a fringe of fine teeth on the 

 inner dorsal margin. This character seems to be of gen- 

 eric value, and the name Deltistes is here proposed for 

 the group typified by Deltistes luxatus. In both Chas- 

 mistes and Deltistes the lower pharyngeals are weak, with 

 numerous small teeth. 



I may further note that Catostomus fecundus Cope, is 

 a species of Chasmistes, and that the genus Lifiomyzon 

 Cope, cannot be separated from Chasmistes. 



The known species of Chasmistes may be thus distin- 

 guished: 



a. Scales moderate, 60 to 65 in lateral line. 



b. Mouth small; nose with a prominent hunip, formed by the exten- 

 sion of a small " pre-nasal " bone between the bases of the premax- 

 illary spines; scales 8-64-9; dorsal rays 11. Utah Lake. 



fecundus Cope. 

 bb. Month large; hump on snout rather less prominent; lips thinner 

 and smooth. 



c. Scales 10-62-9; dorsal rays 11. Utah Lake, liorus Jordan. 

 cc. Scales 13-65-11; dorsal rays 12; head very wide. Pyramid 

 Lake. cujus Cope. 



aa. Scales small, 72 in lateral line; snout short, without prominent hump; 

 cranial surface smooth; scales 12-72-11; dorsal 11; mouth rather small. 

 Klamath Lake. breviroslris Cope. 



Proc. Cal. Acad. Sci., 2d Ser., Vol. VI. June 27, 1896. 



