MAY, 1902 THE ICHTHYOLOGY OF MEXICO MEEK. 117 



sub-species. In the specimens from Zirahuen the teeth are smaller 

 and usually in bands, rather than in two series; vomerine teeth 

 usually present. 



The anterior part of the head in a few specimens from Patz- 

 cuaro is nearly black, that of others is dark, while that of most is 

 very light. Base of anal ij in head, its rays 18 to 20; scales 

 70-17; gill-rakers 5 + 21 = 26; vertebrae 23-1-20 = 43. This species 

 reaches a length of about 1 1 inches. It is an excellent food fish. 

 Abundant. Xochomilcho; Patzcuaro; Zirahuen. Lago de Cha- 

 pala is the only other locality from which this species is known. 



MELANIRIS, gen. nov. 



Type, balsanus. 



This genus differs from Chirostoma in having a rounded lower 

 jaw, a longer anal fin, a short caudal peduncle, and in having the ori- 

 gin of the spinous dorsal fin behind that of origin of anal fin. In all 

 of the specimens the iris is black. In Chirostoma it is silvery. 



Peritoneum black, alimentary canal shorter than total length of 

 the fish. Vertebrae 17+19 = 36. 



Melaniris balsanus, sp. nov. 



Type, No. 3706, F. C. M. Length, 2.68 inches. 



Locality, Rio Balsas, Balsas, Guerrero, Mexico. 



Head \\; depth 5^; D. iii-g: A. 21; scales 39-10. Body 

 elongate, slender, not much compressed; snout rounded laterally; 

 mouth small, lower jaw slightly the longer; caudal peduncle very 

 short. Dorsal fins posterior, origin of spinous dorsal considerably 

 behind origin of anal fin, and midway between base -of caudal fin 

 and posterior margin of opercle; outer row of teeth large, canine- 

 like, wide apart; behind these a band of small villiform teeth; base 

 of anal \ longer than head, its rays varying from 20 to 23; dorsal 

 spines 2 to 4, usually 3; pectoral fin high on sides of body, its length 

 \\ in head; ventrals 2^; gill-rakers 4+13=17; vertebrae 17+19 

 = 36; scales large, with entire margins. Olivaceous, rather 

 opaque, dorsal region finely punctulate with black. A well 

 defined silvery band on sides. 



Very abundant in Rio Cuculo and the Rio Balsas, at Balsas. 

 A small species seldom reaching a length of 2\ inches. It 

 appears firmer as to its flesh than any of the species Chirostoma. 

 Ovaries large, evidently nearing the spawning time. The ovaries 

 of this species taken April 22 and 23 are much larger than those 



