NATURAL SCIENCES OF PHILADELPHIA. 



281 



This fish is more compressed posteriorly, has a larger head and eye, and 

 more projecting under jaw than the S. elongatus. 



It resembles an Aspius no little, but differs in the shorter anal, and fewer 

 pharyngeal teeth. The Alburnus acut us, badly described by Lapham, is 

 evidently an allied species. 



Two specimens ; exact locality in Michigan not stated. 



Since the above was penned, I have found that Bleeker (in Comptes Ren- 

 dus xv. 1863,) has united the genera which I have attached to Squalius to 

 Aspius, placing Squalius with Teleates, Scardinius and Cyprinella as syno- 

 nymes of Leuciscus. That Squalius and Telestes are identical, I fully believe ; 

 but if Cyprinella and Scardinius are not different from Leuciscus our ideas 

 of characters must undergo a change. 



Plargyrus americanus. 



From Saginaw Bay, No. 253, and a variety from Grosse Isle, Detroit River, 

 distinguished by its very elongate form, especially in regard to its caudal pe- 

 duncle. Scales |46 ; that is, two rows less above the lateral line than in many 

 high-bodied specimens ; there are others quite intermediate. 



Chrosomus e o s Cope, Proc. Acad. Nat. Sci., Philadelphia, 1861, 523. 



From New Hudson, Liviugston County, from streams flowing into Lake 

 Erie. Larger specimens of this species exhibit a short lateral line, though in 

 many it is wanting. Its points of separation from erythrogaster are as 

 follows : 



ery throgaste r. 



Head less than one-fourth length to 

 base of caudal. Head narrower ; pa- 

 rietal width one-fourth distance from 

 base of first dorsal ray to base of 

 caudal, which is equal from first dorsal 

 ray to nares. 



Muzzle longer, overhanging, angle 

 of mouth opposite nares. 



Scales above lateral line 24 rows. 



e o s. 



Head more than one-fourth do. Head 

 broader ; parietal width one-third from 

 first dorsal ray to caudal, which equals 

 from dorsal to posterior margin of or- 

 bit. 



Muzzle shorter, mouth more oblique, 

 reaching edge of orbit. 



Scales above lateral line 18 rows. 



Alburnops heterodon. 



A species having the general structure of Alburnops, and pharyngeal teeth 

 usually, but not always, presenting its characteristic masticatory surface. 

 They have sometimes a trace of the creuulation pertaining to Cyprinella, and 

 are arranged usually in but one row of four on each side, which is sometimes 

 accompanied by a single tooth of the inner row. This species is, therefore, 

 allied to Codoma, Cyprinella and Squalius. Scales f 36, with about eleven 

 distant radii on the rather broad exposed surface. Fissure of mouth not 

 reaching line of orbit. Head one-fourth of length to base of tail, a little 

 greater than greatest depth. Diameter of eye one-third of length of head. 

 Operculum higher than long. Outline from end of muzzle to base of dorsal 

 greatly ascending. Greatest breadth of head one-fourth of the distauce from 

 end of muzzle to base of dorsal. Dorsal high ; the bony ray long ; its front 

 ray to the hinder as 2- to 1, and contained 2i times in the distance from its 

 base to the origin of the caudal fin : like the ventrals, it is nearer the end of 

 the muzzle than the base of the caudal. Ventrals reaching anus ; pectorals 

 falling much short of ventrals. Rays, D. 48 ; A. 8 ; V. 8. 



Length two and a half inches. 



Above yellowish-brown ; the scales darker bordered ; below yellowish- rosy, 

 or sometimes goldeD. A dark lateral band from end of muzzle to tail, which 

 is covered on the sides by a silver band with blue reflections. 



Numerous specimens from Lansing ; others from Grosse Isle. 



1864.] 



