THE CYPRINODONTS. 85 
Gambusia gracilis. 
Plate IV. Fig. 6, teeth. 
Tiphophorus gracilis Heck., 1852, Sb. Ak. Wien, I, 300, pl. IX, fig. 3-4. 
Hemiziphophorus gracilis Blk., 1860, Cypr., 480. 
Gambusia Heckeli Blk., 1860, Cypr., 485. 
Gambusia gracilis Gth., 1866, Cat., V1, 336; Eig., 1893, P. U. S. Mus., XVI, 57. 
Heterandria nobilis B. & G., 1854, P. Phil. Ac., V1, 390. 
Gambusia nobilis Grd., 1859, P. Phil. Ac., 121,— Mex. Bd. Sur., Fish., 71, pl. 39, fig. 8-11; Blk., 
1860, Cypr., 485; Gth., 1866, Cat., VI, 335; Jor. & C., 1877, B. Buf. Soc., IIT, 142; Jor., 1878, B. U. S. 
G. Sur., IV, 433, — 1887, R. U. 8. F. Com., 838; Jor. & G., 1882, B. 16 U. 8. Mus., 346; Woolm., 1894, 
B. U.S. F. Com., 60. 
Gambusia speciosa Grd., 1859, P. Phil. Ac., 121; Jor. & C., 1877, B. Buf. Soc., ITT, 142. 
Zygonectes speciosa Blk., 1860, Cypr., 486. 
Gambusia senilis Grd., 1859, P. Phil. Ac., 122; Trosch., 1865, Verz. Wirb. Mex., 106; Jor. & C., 
1877, B. Buf. Soc., III, 142; Jor. & G., 1882, B. 16 U. S. Mus., 894; Jor., 1887, B. U. S. F. Com., 838, 
Zygonectes senilis Blk., 1860, Cypr., 486; Trosch., 1865, Verz. Wirb. Mex., 106. 
Gambusia nicaraguensis Gth., 1866, Cat-, VI, 236, —1868, Tr. ZS. L., VI, 483, pl. 82, fig. 3; Gill, 
1877, P. Phil. Ac., 187; Eig., 1893, P. U. S. Mus., XVI, 57. 
Gambusia infans Woolm., 1894, B. U. S. F. Com., 62. 
B. 6; D. 9 (sometimes 10 or 8); A. 11-10; V.6; P. 13-14; Ll. 30-33; 
Ltr. 9-8; Vert. 14+17. 
Female shorter and deeper than G. Holbrookii. Head or depth about one 
fourth of the length to the base of the caudal. Crown slightly convex. 
Snout as long as eye, broad, blunt. Eye as long as snout, two thirds of fore- 
head, two sevenths of head. Mouth wide ; lower jaws longer, firmly joined ; 
upper short, protractile. Chin steep. Teeth conical, in bands, outer series 
larger. Dorsal origin little behind mid length, little backward of that of 
anal. Caudal short, deep, convex on hind margin. Scales, large, broad, 
short. The proportions in length of head or depth vary greatly in the dif- 
ferent sizes and sexes. Usually the hook on the anal process is slight. 
Brownish olive, light to dark or brown, edges of scales darker, belly 
lighter to silvery, lower surface of head silvery to brownish, crown dark 
with or without a small whitish spot. Small to medium sizes have a some- 
what darker longitudinal band on the middle of the flank in which there is a 
dark line. On larger females the coloration is nearly uniform brown in which 
the band on the flank is hardly visible. Fins dusky, darker outward, or with 
faint transverse cloudings. Males from Monclova, Mex., have a very light 
ground color, dark edged scales, a blackish crown with a small but distinct 
white spot, a blackish vertebral line, a blackish band from the upper angle of 
the operculum to the middle of the tail, and a black line in the lateral band. 
The dark edges of the scales are blacker and wider in the band on the 
flanks. Mexico to Central America. 
