1856.] 187 



The pliaryngeal bones are expanded upon their curvature. The teeth are of the 

 prehensile li^ind of the hooked tj'pe, provided with a grinding surface ; strongly 

 hooked, and disposed thus : 4 4, that is, upon one single row of four. 



Now, comparing the above with the characters assigned to Argyreus^ we find 

 that the most prominent difference resides in the pharyngeal teeth. The isth- 

 mus is narrower, and the insertion of the ventrals placed further back. 



1. Agosia chrysogater, is about three inches and a half in total length, the 

 head forming a little more than the fifth of it. The posterior extremity of the 

 maxillary extends to the vertical line of the anterior rim of the orbit. The eye 

 is large and circular, its diameter being contained about four times in the length 

 of the side of the head. The anterior margin of the dorsal is a little nearer the 

 end of the snout than the insertion of the caudal. The following is the formula of 

 the fins : 



D 10 ; A 7 ; C 4, 1, 9, 8, 5, ; V 9 ; P 16. 



A minute rudiment at the anterior margin of both the dorsal and the anal fins 

 are not included in the above numbers. 



The region above the middle of the flanks is reddish brown, spotted or dotted 

 with black, especially upon the head ; a black vitta separates this region from 

 that beneath, which is unicolor of a golden hue. 



The species was collected in the Rio Santa Crux, Sonora, by John H. Clark, 

 under Col. J. D. Graham. 



2. Agosia metallica. The specimens of this species are a little shorter than 

 those of the preceding one. It is very characteristic, and easily distinguished 

 from its congener. The head is shorter and the snout more abruptly rounded. 

 The eye is smaller also. The body is more gracefully subfusiform and com- 

 pressed. The dorsal is higher and narrower, rounded superiorly. The posterior 

 margin of the caudal is crescentic, less furcated than in A. chrysogaster. 



The formula of the fin's rays present also some difference: 



D 9 ; A 8 ; C 4, 1, 9, 8, 1, 5 ; V 8 ; P 15. 



The same is true with regard to the rudiment at the anterior margin of the 

 dorsal and anal, and which must be sought for under the skin. 



Upper regions greyish brown dotted with black ; inferiorly silvery and uni- 

 color ; a black vitta on the sides separating the two hues. 



Collected by John H. Clark, under Col. J. D. Graham, U. S. A., in the Rio San 

 Pedro, an afiluent of the Rio Gila. 



The genus which we have formerly characterized under the name of 



POGONICHTHYS, 



although enlarged by the accession of a new species, stand within the same 

 limits as were originally assigned to it. The body is fusiform and elongated, 

 compressed, covered with large and uniform scales, and provided with a con- 

 spicuous lateral line deflexed upon the middle of the abdomen. The dorsal fin 

 is higher than long ; the ventrals are inserted in advance of the anterior margin 

 of the dorsal. The caudal is bifurcated. The head is of moderate size or else 

 small, either rounded or flattened upon its upper surface. The snout being 

 more or less protruding beyond the lower jaw, the mouth assumes a somewhat 

 inferior position, although opening horizontally forwards. The mouth itself is 

 of medium size, provided upon its angle with a barbel inserted upon the ante- 

 rior edge of the posterior extremity of the maxillary. The eye is of moderate 

 development. The isthmus is quite narrow. The pharyngeal bones are pro- 

 portionally stout, the inferior limb being, however, slender, slightly arched and 

 expanded upon its symphysis. About tlie height of the third tooth the con- 

 vexity suddenly expands, tapering off towards the extremity of the upper branch, 

 which is slightlj'' bent inwardly downwards. The teeth are well developed, very 

 much compressed upwards and hooked. They are of the prehensile kind, of 

 the hooked type, with a grinding surface, somewhat inclined backwards, and 

 disposed upon a double row of two and four : 2 | 4 4 | 2. 



