188 [September, 



This genus is intimately related to Leucosomtis, differing from it chiefly, by 

 the structure of its teeth, which are provided with a grinding surface in Pogo- 

 nichthys, whilst there is a sharp edge in Leucosomus. 



1. PoGONiCHTHYS IN^QUILOBUS, B. & G. Proc. Acad. Nat. Sc. Philad. vii. 

 1854, 136. 



Besides the specimens collected by Dr. Heermann in the San Joaquin River, 

 Cal., we have received others from Petaluma, Sonoma County, Cal., collected by 



E. Samuels. 



2. PoGONicHTHYS SYMMETRicus, B. & G. Proc. Acad. Nat. Sc. Philada. vii. 

 1854, 136. 



From Fort Miller, San Joaquin Valley, Cal. ; collected by Dr. Heermann. 



3. PoGONiCHTHYS ARGYREiosDS, Girard, Proc. Acad. Nat. Sc. Philada. vii. 

 1854, 153. 



Collected at Presidio, near San Francisco, Cal., by Lieut. "W. P. Trowbridge, 

 U. S. A. 



4. PoGONiCHTHYS COMMUNIS. This spccies is the most characteristic of the 

 genus, by its small and flattened head and the large scales which cover the 

 body. The mouth is larger in proportion than in any of its congeners ; in large 

 specimens the snout overlaps entirely the lower jaw, in which respect it resem- 

 bles Gila elegans most remarkably. The barbel upon the angle of the mouth is 

 very conspicuous. The fins are all well developed ; the external rays of the 

 pectorals extend beyond the usual termination of these fins in other species. 

 The dorsal region is reddish grey or greyish red, according to circumstances ; 

 the rest of the body whitish yellow or yellowish golden, the fins being unicolor. 



"We have examined numerous specimens of this species. They were collected 

 at Fort Pierre, Nebr., by Dr. John Evans ; at Fort Union, by E. J. Denig ; above 

 Fort Union and in Milk River, by Dr. Geo. Suckley, under Gov. I. I. Stevens ; in 

 the Yellowstone River, by Dr. F. V. Hayden, and in the Sweet Water, a tributary 

 of Platte or Nebraska River, by the late J. Soule Bowman. 



The genus of genuine Gudgeons, 



GoBio, Cuv. 



is a type that may easily be characterized. Head subconical, with the snout 

 rather thick and obtuse, overlapping the lower jaw, thus giving the mouth a 

 somewhat inferior position. The latter, however, is directed forwards ; it is 

 large, and provided with a well developed barbel upon the posterior extremity 

 of the maxillary. The eye is of moderate development. The isthmus is large. 

 The body is elongated, subcylindrical. The dorsal and anal, both, are rather 

 narrow fins. The insertion of the ventrals takes place under the anterior margin 

 of the dorsal or a little behind it. The caudal is bifurcated. The scales are large 

 and the lateral line nearly median. The pharyngeals are gracefully curved, the 

 upper and lower branches tapering, the convexity very slightly expanded. The 

 teeth are slender, subcylindrical upon their base, compressed above, of the rap- 

 tatorial kind of the hooked type, without grinding surface, and disposed 

 upon a double series of one, two or three, and three, four or five, as follows : 

 3 I 55 I 2, or 2 | 44 | 1, &c. &c. 



This genus may be distinguished from Leucosomus by its protruding snout, 

 much more developed maxillary barbel, and narrow dorsal and anal fins, and 

 finally its pharyngeal teeth more strongly hooked. 



1. GoBio GELIDU8. Body and head very slender and elongated; head forming 

 about the fifth of the total length. The snout is quite prominently developed. 

 The eye is rather small compared to G. Jiuvialilk, resembling more, in that re- 

 spect, G. cataractce, from which, however, this species can readily be distin- 

 guished by the position of its ventral fins, which are inserted under the anterior 

 margin of the dorsal, whilst they are placed in advance of it in G. cataractce. 



