(572 



ZOOLOGY FISHES. 



Total length, 0.060 ; length to basis of caudal, 0.048 ; length to first dor- 

 sal ray, 0.025. Color dark-olive ; a blackish lateral band ; scales above it 

 edged with dusky ; a black vertebral band ; head, except lower aspect, 

 black ; anterior border of pectoral, both borders of anal, and a strong 

 median band through the dorsal fin, black. 



Several specimens from the Arkansas River at Pueblo, Colo., from C. 

 E. Aiken. 



Numerous individuals from the same locality differ in having a less 

 truncate muzzle and a much smaller anal fin ; the radial and scale formulae 

 are the same. I suppose these to be females of the present species. 



HYBOGNATHUS, Agass. 

 HYBOGNATHUS NUCHALIS, Agass. 

 Hylognallms niichalis, COPE, Proc. Am. Phil. Soc. Phila., 1870, 466. 



Abundant in the Rio Grande ; one of the few eastern species occurring 

 west of the Rocky Mountain range. 



CAMPOSTOMA, Agass. 

 CAMPOSTOMA AIKENII, Cope, up. nov. 



A true species of this genus, exhibiting the characteristic convolution 

 of the alimentary canal around the natatory bladder, from the Upper 

 Arkansas River, is represented by a small specimen. Form attenuated ; muz- 

 zle conic ; mouth terminal, small. Head 3.75 times in length without caudal 

 fin; depth 4.75 times in the same. Eye 4.25 times in head, 1.5 times in 

 both interorbital width and length of muzzle. The fissure of the mouth 

 only reaches to the anterior nareal opening. The fins are small, the dorsal 

 stending immediately over the ventral. Radii : D. I. 8 ; A. I. 7. Total 

 length, 0.052 ; length to origin of caudal fin, 0.042 ; to basis of dorsal fin, 

 0.022. Color above dusky-olive ; a dark lateral band from end of muzzle 

 to base of caudal fin ; below silvery. 



