196 [September, 



of dorsal fin, or a little behind it. Dorsal and anal Ens without strongs and un- 

 divided ray anterior!}'. Scales very large, imbricated, much higher than long. 

 Lateral line forming a downward curve beneath the middle of the flanks. Pha- 

 ryngeal bones rather slender with an angular expansion at the upper portion of 

 the descending branch, the expansion itself tapering away towards the upper 

 and inner extremity. The teeth are compressed, of the prehensible kind, of the 

 hooked type, very slightly hooked, provided with a grinding surface ; being dis- 

 posed upon a double row as follow: 2 | 4 4 | 2. 



The teeth of this genus are figured by Heckel, under the name of Argyreus 

 ruhrijyinnis, the second species of his genus Argyreus, and which is nothing else 

 but Plargyrus cornutus in a breeding dress. 



The species are : 



1 Plargyrus cornutus. Cyprinus cornutus, Mitch. See Siorcr^s Fishes of 

 Mass. in Mem. Amer. Acad. v. New Ser. 1855, 118, where this species is figured 

 and described. 



2. Plargyrus typicus. Rutilus plargyrus, 'B.kvw. Ichth. Ohiens. 1820, 50. 

 Leuciscus plargyrus, Kirtl. Storer, Synops. 1846, 158. 



3. Plargyrus gibbosus. Leuciscus gibhosus, Storer, Proc. Bost. Soc. Nat. 

 Hist, ii., 1845, 48; Synops. 1846, 166. 



Alabama. 



4. Plargyrus frontalis. Leuciscus frontalis, AgaSS., Lake Sup. 1850, 368 

 PI. iii. fig. 4. 



Lake Superior. 



5. Plargyrus gracilis. Leuciscus gracilis, Agass., Lake Sup. 1850, 370' 

 Lake Huron. 



6. Plargyrus. BOWMANi. We inscribe this species to the memory of one, who, 

 under difficulties of various sorts, during a travel across the continent, thought 

 it not of little importance to collect and preserve specimens of natural his- 

 tory, which he forwarded to the Smithsonian Institution. The species is grace- 

 fully subfusiform in its profile, the depth in advance of the dorsal being equal 

 to the fifth of the entire length, in which the head itself enters about four times and 

 a half The eye is very large ; its diameter being contained a little less than 

 four times in the length of the side of the head. Dorsal region reddish brown ; 

 sides silvery, abdomen yellowish. A black streak along the flanks and above 

 the lateral line. 



A specimen, four inches in total length was caught in the Sweet water, a 

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



Had the name of ITypsolepis not been made synonymous of Plargyrus, we 

 might have applied it with perfect propriety to the group which we now call 



CYPRINELLA, 



since the fishes therein included, possess that curious character of scales higher 

 than long. They replace in the South-west, the Plargyri of more northern 

 climes. Though generally smaller than the species of Plargyrus, some do re- 

 semble the latter in a very striking manner, whilst others are much shorter and 

 deeper in proportion. The chief differences between the present genus and 

 Plargyrus, is to be found in the pharyngeal teeth and the position of the ventrals. 

 To Jfoniana it bears more striking resemblances and real aflSnities. The 

 position of the ventral fins is the same, the pharyngeal bones are alike also, the 

 teeth are of the same general pattern, but disposed upon a double series in Cypri- 

 nella, and upon one only in iVoniana. Besides, in Cypri?iclla, the snout generally 

 protrudes beyond the lower jaw, though the mouth is slightly oblique and sub- 

 terminal. But let us formulate the generic characters of the genus we are now 

 treating of: Body very compressed, either elongated and subfusiform, or else 

 with the dorsal and abdominal outlines rather arched, but which may, after all. 



