180 CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY III. 



Specimens in United States National Museum. 



Genus PANTOSTEUS Cope. 



Minomm COPE, U. S. Geol. Surv. Wyoming, 1870, 434 (1872). (Not of Girard.) 

 Pantosteus COPE, Lieut. Wheeler's Expl. W. 100th Mer. v, C73, 1876. 

 Catostomus, Acomus et Minomus sp. GIUA.RD. 



Type, Hinomus plalyrhynclius Cope. 



Etymology, TTUV, all ; oariov, bone (from the closing of the fontanelle by bono). 



Head moderate or rather small, 4 to 5 times in length of body, flattish 

 and rather broad above, anteriorly somewhat pointed ; eye rather small, 

 usually behind the middle of the head : suborbital bones narrow, as in 

 Catostomus ; bones of head rather thick, the two parietal bones firmly 

 united, entirely obliterating the fontanelle. , 



Mouth rather large, entirely inferior ; each jaw with a more or less, 

 developed cartilaginous sheath, separable in alcohol, essentially as in 

 Chondrostoma, Acrochilus, and related genera; upper lip broad, papillose, 

 with a rather broad, free margin, and several series of tubercles ; lower 

 lip largely developed, with an extensive free margin deeply incised 

 behind, but less so than in Catostomus. m Pharyngeal bones and teeth 

 essentially as in Catostomus. Isthmus quite broad. 



Body generally elongate, subterete, and little compressed. 



Scales quite small, from 80 to 105 in the course of the lateral line, 

 and 30 to 35 in a cross series between dorsal and ventrals, usually more 

 or less reduced in size and crowded forward, as in Catostomus ; lateral 

 line well developed, straightish. 



Fins generally rather small ; first ray of dorsal usually about midway 

 of body, its rays few, 9 to 12 in number ; ventrals inserted rather under 

 posterior part of dorsal, their rays 10 or 9 ; anal short and high, with 

 7 developed rays; caudal rather shallow, emarginate ; pectorals well 

 developed : air-bladder with two chambers. 



The characters of Pantosteus are essentially those of Catostomus, except 

 that the fontanelle is obliterated. The usual scale-formula is interme- 



