1856.] 195 



small. The scales are of medium size, higher than long, and the lateral line is 

 but slightly deflesed upon the thoracic region. The pharyngeals are moderately 

 expanded upon their convexity. The teeth are of the raptatorial kind, of the 

 hooked type, compressed, without grinding surface, instead of which, a sharp, 

 but not serrated ridge. They are arranged upon one single row of four, thus : 

 44. 



The general physiognomy of the genus reminds us of that of Pimcphales and 

 Cochlognalhus, with which genera it has no intimate affinities, when the pharyn- 

 geal dentition is taken into consideration. Indeed, its affinities with Cyprinella 

 and Moniana are of a more close character, for the teeth are constructed according 

 to the same general pattern ; from Cifprinella, however, it differs by the presence 

 of one single row of teeth, and from Moniana by the absence of serratures upon 

 the cutting edge of the teeth, and finally from both Cyprindla and 3Ioniana by 

 smaller scales, the course of the lateral line, and the short and rounded head. 



1. CoDOMA ORNATA. This species has the aspect of Pimpephales promdas to a 

 much higher degree than the following. The head forms the fifth of the total 

 length, whilst the greatest depth enters in the latter but three times and a half. 

 The eye is circular and well developed ; its diameter entering a little over three 

 times in the length of the side of the head. The anterior margin of the dorsal 

 is a little nearer the extremity of the snout that to the insertion of the caudal 

 fin. 



D 8 +1 ; A 7 + 1 ; C 6, 1, 9, 8, 1, 6 ; V 7 ; P 12. 



The coloration is rich and profuse, the upper regions are purplish black, with 

 transverse bands of the same hue along the flanks to the base of the caudal fin ; 

 the space not occupied by these, on the back as well as on the abdomen, is of 

 a golden red. The fins are purplish black, edged or tipped with golden yellow 

 or pure white. 



Inhabits Chihuahua river and its tributaries ; collected by John Potts, Esq. 



2. CoDOMA viTTATA. Has a more elongated body and subfusiform outline 

 than the preceding species. The head forms a little less than the fifth of the 

 entire length, whilst the depth enters in it about four times and a half. The eye 

 is much smaller than in C. ornaia; the fins and scales are smaller, also. 



D8 + 1; A7+2; C7, 1, 9, 8, 1, 6; V7; P14. 



The upper regions are purplish brown ; a silvery band along the middle of the 

 flank; inferiorly yellowish orange. Fins unicolor ; the superior ones greyish, 

 the inferior yellowish. 



Collected in the valley of Mexico, by John Potts, Esq. 



Since Rafinesque's genera are to be restored, Ms genus 



Plargyrus, 



is to take the precedence over the genus Hypsolepis of more modern coining. The 

 name of Plargyrus was provided for in the Ichthyologia ohiensis, to replace that 

 of Ruidics in the eventuality that Cyprinus riUilus of Europe, which was the type 

 of the genus Ruiilus, should prove generically distinct from Rutilus plargyrus and 

 similar American species, and which is the case. _ 



The genus Plargyrus includes the prettiest species of American Cyprinoids. 

 Their comparatively small size, compressed and graceful body, subfusiform m 

 its profile, added to brilliant and vivid colors, have brought these fishes to the 

 notice of the multitude. They are commonly known as " Red Dace," " Silver- 

 side Fall-fish," " White and Yellow-winged Shiner," " Shiner," &c. 



Its generic traits may be thus expressed : Head large and subconical ; mouth 

 terminal more or less oblique upwards. Jaws equals. No cirrhi or barbels. 

 Eyes large. Isthmus quite narrow. Tail tapering. Caudal fin bifurcated or 

 forked The insertion of the ventrals is situated opposite the anterior margin 



