208 CYPRINIUiE. 



Chub, and Roach are referred to distinct genera, cannot be to the 

 advantage of science. In the following synopsis of species I retain 

 the New-World species in a separate category. This is an imper- 

 fection which I am unable to avoid, in consequence of our present 

 incomplete knowledge of this fauna. The natural history of North 

 American freshwater-fishes is in its infancy, and only a small pro- 

 portion of the literature pertaining to it has been critically examined ; 

 and this is a task which cannot be successfully undertaken without 

 a very extensive series of examples from the various systems of 

 rivers. 



Synopsis of the Species. 



I. Old- World species. (For doubtful species see note *, p. 209,^ 



A, Pharyngeal teeth in a single series. 



1. Anal tin with at least ten rays ; dorsal fin opposite to the ventral? 



{Leuciscus), p. 212. 



2. Anal fin with nine rays ; dorsal fin inserted behind the ventrals 



{Pseudophoxinus), p. 220. 



B. Pliaryngeal teeth in a double series. 



1. Lateral line complete (Squalius, Idus, Scardinius, Telestes), p. 220. 



2. Lateral line incomplete : Phoxinus, p. 237. 



II. New- World species. (For doubtful species see note t, p. 209.) 



A. More than fifty scales in the lateral fine. 



1. The dorsal fin commences above, or but sUghtly in advance of, the 



root of the ventrals. 



a. Pharyngeal teeth in two series, p. 239. 



h. Pharyngeal teeth in a single series {Alganseu), p. 244. 



2. The dorsal fin commences behind the root of the ventrals, rudi- 



mental caudal rays not unusually developed. 



a. Pharyngeal teeth in two series. 



aa. Lateral line complete ; pharyngeal teeth 5 or 4 . 2 — 2 . 4 or 5 



(Cli}iostomus) p. 245. 

 hb. Lateral line complete ; pharyngeal teeth 3 . 1 — 1 . 3 [?](7'«Vr- 



roga), p. 247. 

 cc Lateral line incomplete {Phoxinus, sp.), p. 247. 



b. Phaiyngeal teeth in a single series {Pseudophoxinus, sp.), p. 247. 



3. The dorsal fin commences behind the root of the ventrals. 



Iludimental caudal rays much developed. Pharyngeal teeth in 

 a single series (Lavinia), p. 248. 



B. Fifty or less scales in the lateral line. 



1. Pharyngeal teeth in two series. 



a. Origin of the dorsal fin opposite to the ventrals, p. 249. 



b. Origin of the dorsal fin distinctly behind the ventrals, p. 2r)4. 



2. Pharyngeal teeth in a siujilc scries {Moniana), p. 258. 



