gS Field Columbian Museum — Zoology, Vol. III. 



and Santa Maria have a dark dorsal fin, but in many specimens 

 the outer anterior half is very light. In the darker males, from 

 all places, all of the fins except the dorsal are margined with 

 black, the broader margins being on caudal and last anal rays. 

 I agree with Mr. Garman in uniting C. exi/iiii/s with C. elegans. 



The females have a black spot on middle of the last dorsal rays. 



This species spawns during the first half of July. 



Very abundant in Northern Mexico. Colonia Juarez: Guz- 

 man; Santa Maria; San Jose; Ahumada: Chihuahua: San Andres: 

 Minaca; Santa Rosalia; Jimenez. 



Pseudoxiphophorus bimaculatus (Heckel). 



This species has the general appearance of Gaiiihusia. It has 

 a larger dorsal and the less advanced position of the anal fin 

 than do species of Gai)ibusia. It also reaches a larger size. 



The largest female is 3.20 inches in length. The largest male 

 is 2. 24 inches in length. As in Gatnbiisia, the males are reported to 

 be much less numerous than the females. They are much smaller 

 and much less liable to be captured than are the females, so that 

 the proportion of males to females found in collections is no true 

 indication of that which really exists. 



Peritoneum blackish: intestine short, shorter than the length 

 of the fish; teeth conical, curved backward and in broad bands 

 in each jaAV, those on the lower jaw being the larger: lower jaw 

 the longer. 



Viviparous: one female 2.81 inches in length contained 48 

 eggs, each about j^^ inch in diameter, 42 of Avhich had the eye 

 spots formed, 6 showed no eye spots. These specimens were 

 taken May g. The time of depositing their young is probably 

 near the first to the middle of June. 



This species was very abundant at Jalapa, where it was found 

 with XipJiopliorus jalapcv. Jalapa. 



GAM BU SI A Poey. 



So far as known this genus is represented in Mexico by three 

 species, G. affi/iis from the Rio Grande Basin, G. infans from the 

 Lerma Basin, and G. gracilis, found in streams on both sides of 

 the divide south of Mexico City. 



Gambusia affinis (Baird cV Girard). 



.■\ faint brownish band on sides; dorsal and especially the anal 

 fin with much black, the anal being darker on the distal half. 



