1856.] 179 



The ten species that precede as well as the four following ones, are amongst 

 those whose history has most perplexed us. At last we were glad to recognize 

 the genus 



Hybortnch03, Agasa. 



established upon a species of the Ohio and its tributaries, and believed to be 

 Minnilus notattis of Rafinesquc. We have examined carefully the latter species, 

 and after a series of comparative studies we were enabled to add the following 

 few species to the genus which we thus characterize : Head rather short, upper 

 surface depressed ; snout abruptly truncated and rounded. The mouth is of 

 medium size, subterminal, its cleft being horizontal, the lower jaw flattened and 

 thin, rounded upon its periphery and slightly overlapped by the snout. There 

 are no barbels at the angles of the mouth, which do not reach a vertical line 

 drawn in advance of the orbit. The eyes are large ; the isthmus is of moderate 

 width. Anterior ray of dorsal fin shorter than the second. The insertion of 

 the ventrals is situated opposite the anterior margin of the dorsal or in advance 

 of it. The caudal is furcated. The scales are large, higher than long ; the 

 lateral line follows the middle of the flanks. The pharyngeal bones are slender, 

 and more so upon the inferior limb, which is longer than the upper and curved 

 backwards and sideways, whilst the upper limb is gently curved inwards. The 

 convexity of the same bone is expanded. The teeth are of the cultriform kind 

 of the grinding type, very much compressed, slightly hooked, and consequently 

 provided with quite a narrow grinding surface. Their disposition is upon a 

 single row of four : 4 4. 



1. Hyborhynohus perspicuus. The head is contained five times and a quarter 

 in the total length, instead of constituting the sixth part of it, as in II. nolatus. 

 The mouth and eye, both, are a good deal larger than in the latter. The inser- 

 tion of the ventrals is situated immediately under the anterior margin of the 

 dorsal. The caudal fin is more deeply furcated than in H. notatus. 



D 9+2; A 7-1-2 ; C 10, 1, 9, 8, 1, 8 ; V 9 ; P 14. 



There is a very minute rudimentary ray at the anterior margin of both the 

 dorsal and anal, followed by a second, alaout half the height of the fin. 



Upper region and flanks reddish ; abdomen sulphur yellow ; lateral line dotted 

 with greyish purple, more distinct towards the base of the caudal upon which 

 a dark spot exists. Fins yellowish, also with a black spot upon the anterior 

 margin of the dorsal below the middle height. Superior portion of the dorsal, 

 greyish, as also the external margin of the caudal. 



From Arkansas River, near Fort Smith ; collected by Dr. Geo. G. Shumardu 



2. Hybokhynchus tenellus. It is more slender and more compressed tha 

 even II. j^erspiams. The head is very much depressed, subpyramidal were the 

 snout not rounded, hence appearing quite small ; it is contained five times and 

 a half in the total length. The insertion of the ventrals is a little in advance 

 of the anterior margin of the dorsal fin. The eye and mouth are proportionally 

 large, and especially the scales, which are the largest among the hitherto known 

 species of the genus. Color uniform reddish above and on the sides ; yellow- 

 ish beneath. A black spot upon the base of caudal fin. Otherwise the fins are 

 unicolor. 



Collected twenty miles west of Choctaw Agency, by H. B. Mollhausen, under 

 Lt. A. W. Whipple. 



3 Hyborhynohus punicecs. As regards the general aspect, this species is 

 intermediate between //. perspicuus and H. tenellus. It is distinguished from 

 both of these by more developed opercular apparatus and much smaller scales. 

 The color is uniform pale red ; the fins are unicolor, yellowish. 



Specimens were collected in Antelope Creek, a tributary of the Canadian 

 River, by Dr. C. B. Ivennerly, and from Llano estacado, by H. B. Mollhausen, both 

 under Lt. A. W. Whipple, U. S. A. 



4. Hyborhynohus confertus. This species has a short and contracted appear 



