114 FlKI.I) Coi.L'MBIAN Ml'SKl.M ZoOUMiY, \'()I.. III. 



Head 4}; depth 5.}; D. v-io; A. 17; scales 48-12. Body 

 slender, moderately compressed; snout short, pointed, its length 

 3^ in length of head; lower jaw slightly projecting beyond 

 upper; mouth oblique, but less so than in C. chapalce; man- 

 dible 2| in head; diameter of eye 3| in the head; teeth small, 

 numerous, in a narrow band on anterior part of each jaw, becom- 

 ing, laterally, in two series; scales moderately large, edges entire, 

 those at the nape slightly reduced in size; origin of spinous 

 slightly nearer tip of snout than base of caudal; base of anal fin 

 i^ in length of the head; pectoral i; ventral 2\; gill-rakers 

 4+21=25. 



Light olivaceous, translucent, lateral band narrow. 



Species of small size, less than 4 inches in length. Seven 

 specimens from Lago de Patzcuaro. Apparently scarce. 



This species resembles C. chapalce, from which it differs in hav- 

 ing a less oblique mouth, a shorter anal fin and a less compressed 

 body. Patzcuaro. 



Chirostoma zirahuen, sp. -nov. 



Type, No. 3609, F. C. M. Length. 3.55 inches. 



Locality, Lago de Zirahuen, Zirahuen, Michoacan, Mexico. 



Head 4-}; depth 5-; D. v-io; A. 13; scales 54-12. Body 

 elongate, nearly terete, less compressed than in any other 

 Chirostoma mouth moderately oblique, lower jaw slightly the 

 longer; length of snout equal to diameter of eye, 3^ in length 

 of the head; interorbital broad, 3 in head; teeth very small, in a 

 narrow band in each jaw. Base of anal fin i .', in head; pectoral 

 i.' { ; ventral 2; scales with entire margins; origin of the dorsal fin 

 nearer tip of snout than base of caudal by a distance greater 

 than diameter of eye; caudal peduncle long and slender; gill- 

 rakers 4 + 17 = 21; vertebra? 23+18 = 41. 



' Dark olivaceous above, lighter below; opaque. This species 

 is one of the darkest found in the Lerma basin. It is the most 

 abundant species in Lago de Zirahuen. 



Species of small size. It is characterized by its dark opaque 

 color, its terete body, the backward position of the dorsal fin, and 

 the short anal fin whose rays are 13 or 14. 



The longest specimen in our collection is 4. 13 inches in length. 

 Abundant in Lago de Zirahuen. Zirahuen. 



Chirostoma humboldtianum (C. & V.) 

 Pescada Blanca. 

 This species is very abundant in the lakes about the City of 



