Occasional Papers of the Museum of Zoology 5 



point near the front margin of the eye, rather than some point 

 in the postorbital part of the head; in coloration; on the 

 average in the larger scales, these being in 32 to 36 instead of 

 34 to 38 transverse series ; and in the shorter gill-rakers, few 

 more than half as numerous as in atripinnis. 



Holotype. — Taken by Dr. S. E. Meek, together with the 

 numerous paratypes, in an upper tributary of the Rio Panuco, 

 at Jesus Maria, Mexico ; an adult male -1:6 mm. long to caudal 

 base ; Cat. No. 5557, Field Museum. Regarding this collection. 

 Dr. Meek (I. c, p. 153) remarks: "There is a small stream at 

 Jesus Maria which belongs to the Rio Panuco system. It is 

 almost without water during the dry season. At the Hacienda 

 a dam is built across the narrow valley forming above it a 

 small lake. In this 4 species of fishes were taken," including 

 the types of G. captiva. The following description is based 

 upon the type, 46 mm. long to caudal- base, and is supple- 

 mented by measurements and counts of five males 40 to 45 mm. 

 long, and of five females, 45 to 49 mm. long. 



The body is deeper and with more arched contours than in 

 G. atripi7inis; the dorsal contour is slightly elevated at the 

 occiput and gradually curved thence to the origin of the 

 dorsal; the ventral contour is deeply curved — more deeply in 

 the female than in the male — from the mouth to the anus, the 

 deepest point in the curve being before the front of ventrals; 

 greatest depth, 2.55 (2.5 to 2.7 in adult male paratypes; 2.6 to 

 2.8 in adult female paratypes ; in young specimens of equal 

 size, the males are a little deeper than the females). From 

 the origins of the dorsal and anal fins the contours of the male 

 converge to the slender caudal peduncle so abruptly that if 

 produced they would meet at an angle of nearly ninety degrees 

 (the contours converge less rapidly in the female, as in that 

 sex the greatest depth is farther forward than in the male; 

 the distance between the origin of the dorsal and of the anal 

 fins is about the diameter of the eye greater in the adult male 

 than in the adult female). Least depth of the caudal 

 peduncle, a little more than half its length behind anal fin ; its 

 length about equal to length of head. 



