202 [September, 



dorsal, and its anterior margin situated anteriorly to the posterior margin of the 

 base of the dorsal, in which respects it differs from Luxilus. The pharyngeal 

 bones are narrow, with a slight expansion upon their convexity ; the teeth being 

 of the raptatorial kind of the hooked type, strongly hooked, without grinding 

 surface, instead of which a sharp but not crenated ridge. They are disposed 

 upon a double row of four or five and two, as follows : 2 | 4 4 | 3, or 2 | 5 

 5 I 2. 



The present genus bears some resemblance to Squalius, from which it may 

 be distinguished by the smooth edge of the dental ridge and the long anal, with 

 its peculiar position in reference to the dorsal. The scales are also smaller and 

 much deeper than long, which is not the case in Squalius. 



1. RiCHARDSONius BALTEATUS. Abramis balteatus, Richards. Fauui Bor. Amer. 

 iii. 1836, 301. Storer, Synops. 1846, 160. 



The specimens before us were collected at Fort Vancouver and Fort Dalles, 

 Columbia River, by Geo. Suckley, under Gov. I. I. Stevens. 



2. RiCHARDSONius LATERALIS, is more of an elongated and fusiform aspect than 

 R. balteatus. The head is contained four limes and a half in the total length. 

 The pharyngeal teeth are five upon the outer row, instead of four. Dorsal region 

 blackish brown ; lower part of sides and abdomen silvery; upper part of sides 

 provided with a black band extending from head to tail. 



Specimens procured at Fort Steilacoom, Paget Sound, "W. T., by Dr. Geo. 

 Suckley, U. S. A., under Gov. I. I. Stevens. 



We adopt the genus 



Luxilus, Rafin. 



To include such species as are congenerical with Leuciscus chrysoleucus of 

 Mitchill, and Luxilus chrysocephalus of Rafinesque. .It is one of the most 

 characteristic genus of North American cyprinoid, and altogether misunder- 

 stood by Heckel ; for, Cyjmnus chrysoleucus^ Mitch., which he places in his 

 genus Lcucosomus, is generally distinct from Lmciscus imlchellus of Storer, as 

 I have had the opportunity to ascertain. The diagnosis given to Leucosomus by its 

 author, and the figures representing the pharyngeal dentition, leave no room for 

 doubt. Leucoso7nus, therefore, is not synonymous with Luxilus, but was really es- 

 tablished upon a species most intimately related to the one yet unpublished, and 

 which is the type of the genus CheiJoncmus. The latter, therefore, must give 

 way to Lcucosomus, a circumstance unavoidable and very much to be regretted, 

 for it complicates the synonymy of both Luxilus and Leucosomus. 



We characterize as follows the genus Luxilus: " Body very much compressed, 

 flattened laterally, and deepest upon the middle of its length. Head propor- 

 tionally small and compressed like the body. Mouth small, terminal, unpro- 

 vided with cirrhi or barbels. Eyes quite large. Isthmus small. Caudal fins 

 forked ; insertion of ventrals situated in advance of the anterior margin of the 

 dorsal. Scales large ; lateral line forming a very open curve, convex down- 

 wards." Pharyngeal bones much stouter superiorly than inferiorly ; a slight 

 expansion may be observed upon the convexity of these bones, extending up- 

 wards. The teeth are of the bruising kind of the hooked type with a slight hook 

 and a well developed grinding surface, both edges of which being strongly 

 crenated. They are disposed upon a single row of five, thus : 5 5. The three 

 uppermost (sometimes the upper two only), stand out in bold relief from the 

 line of the bone. 



We meant to have observed, in speaking of the head, that the lower jaw fits 

 into the upper one when the mouth is shut without protrusion of the snout, and 

 that when the mouth is partly open, the lower jaw aj^pcars longer than the 

 upper. 



1. Luxilus americanus. Cyprinus americanus, Lac'ep. Cyprinus chrysoleucus, 

 Mitch. Leuciscus chrysoleucus, Storer. Leucosomus americanus, Grd. For a de- 



