186 [September, 



of Nebraska, or Platte Eirer. Smaller specimens of the same species were ob- 

 tained in Cottonwood Creek, Utah, by Lieut. E. G. Beckwith, U. S. A. 



Y. Argykeus nubilus. This is a very characteristic species. The head is 

 very small, and the body, fusiform in shape and compressed, is thick and swol- 

 len upon its middle. The tail again is rather slender. The snout is subcorneal, 

 but not more protruding than in the preceding species ; the mouth is a great 

 deal smaller than in the latter, with its barbels less conspicuous. The head 

 constitutes about the fifth of the entire length. The eye is moderately developed 

 and subcircular in shape ; its horizontal diameter is contained about five times 

 in the length of the side of the head. The dorsal, caudal and anal fins are of but 

 moderate development, the pectorals and ventrals rather small. 



D 8+2 ; A 7-f 2 ; C 5, 1, 9, 8, 1, 6 ; V 8 ; P 12. 



The number of rays in the fins does not materiallj^ differ from that of the pre- 

 ceding species ; in both, the anterior two rays of the dorsal and anal fins are 

 mere rudiments. 



The color above is blackish brown, with a purplish hue along the middle of 

 the flanks ; the inferior regions are of a soiled white or yellowish brown. The 

 upper surface of the head and upper half of the sides, including the eye, is deep 

 black ; inferiorly it is whitish or yellowish white. 



Specimens, four inches in total length, were collected at Fort Steilacoom, Puget 

 Sound, W. T., by Dr. Geo. Suckley, U. S. A., under Gov, I. I. Stevens. 



8. Argyreus osculus. Has more the fascies of ^4. atronams than of any other 

 of its congeners, both by the outline of its body and head, and the shape and 

 position of the mouth. The head is comparatively small, forming the fifth of 

 the length, with the exception of the lobes of the caudal. The eye is rather large 

 and subcircular, its diameter entering about four times in the length of the side 

 of the head. The dorsal and anal fins are well developed, the former being 

 convex superiorly, and the latter subconvex exteriorly. The posterior margin 

 of the caudal is crescentic. The posterior extremity of the ventrals extend as 

 far as the vent, which is not the case in the two species described above. 



D 8-1-2 ; A '7-{-2 ; C 5, 1, 9, 8, 1, 6 ; V 8 ; P 14. 



The anterior two rays of both the dorsal and anal fins are mere rudiments, as 

 already stated. 



The color is reddish brown above ; olivaceous on the sides, with numerous 

 dark blotches and dots. Beneath uniform yellowish white or silvery white. 



Many specimens, the largest of which measuring less than three inches, were 

 collected by John H. Clark, under Col. J. D. Graham, U. S. A., in the Baboco- 

 mori, a tributary stream of the Rio San Pedro, itself flowing into the Rio Gila. 



9. Argyreus notabilis. This species resembles A. osculus in many respects, 

 but will always be easily distinguished from it by a more truncated snout, and 

 consequently by a mouth not so deeply cleft. The dorsal fin is situated more 

 anteriorly also. The scales are smallei-. The ground color is yellowish or brownish 

 above, golden or orange beneath, covered all over, the abdominal region ex- 

 cepted, with small black spots. 



Specimens caught in the Rio Santa Crux, Sonora, by John H. Clark, under 

 Col. J. D. Graham, U. S. A. 



The hydrographic basin of the Rio Gila harbors a generic type which, at first 

 sight, one would refer to Argyreus ; but on a closer inspection, its generic traits 

 will appear quite conspicuous. The name of 



AGOSIA 



is proposed for it ; the diagnosis is as follows : Snout rounded, slightly pro- 

 truding beyond the lower jaw, though the mouth opens horizontally. The 

 mouth is of medium size, surrounded with narrow and smooth lips, and pro- 

 vided upon its angle with a very small barbel. The isthmus is of moderate 

 width. The insertion of ventrals is situated opposite the anterior margin of dorsal 

 fin, which is higher than long. The caudal is bifurcated. The scales are minute- 



