THE CYPRINODONTS. §1 
mandibles strong, firmly joined ; intermaxillaries short, protractile. Teeth 
conical, hooked, in bands, outer series larger. Branchiostegal rays six. 
Dorsal large, larger than the anal, originating in the forward half of the 
total length and in advance of the anal in the female. Anal of male farther 
forward and modified into an intromittent organ, Scales large. Intestine 
short. 
The pharyngeal teeth in the specimen dissected are without a shoulder 
(Plate III, Fig. 6, p). Whether this peculiarity is not lost in aged indi- 
viduals can only be determined by further examinations. 
Mexico to Central America. 
Pseudoxiphophorus bimaculatus. 
Plate III, Fig. 6, teeth; Plate VIII, Fig. 9, male. 
Xiphophorus bimaculatus Heck., 1852, Sb. Ak. Wien, I, 297, pl. 9, fig. 1-2. 
Pseudoriphophorus bimaculatus Blk., 1860, Cypr., 485, — 1863, Atl. Ichth., IIT, 140; Trosch., 1865, 
Wirb. Mex., 104; Gth., 1866, Cat., VI, 332; Eig., 1893, P. U. S. Mus., XVI, 57; Woolm., 1894, B. U.S. 
F. Com., 65. 
Paciliodes bimaculatus Steind., 1863, Sb. Ak. Wien, XLVIII, 176, pl. 4, fig 2; Trosch., 1865, Wirb. 
Mex., 104. 
Pseudoziphophorus reliculatus Trosch., 1865, Verz. Wirb. Mex., 104; Gth., 1866, Cat., VI, 333; Eig., 
1893, P. U. S. Mus., XVI, 57. 
B.6; D. 14-15; A. 10-12; V. 6; P. 14-15; Ll. 28-31; Ltr. 8-9; 
Vert. 15+ 17. 
In shape resembling Fundulus heteroclitus. Caudal section deep, strong ; 
back moderately arched. Head depressed, flattened on the crown, one fourth 
of the total length, three tenths of the length to the base of the caudal, more 
than depth. Snout broad, blunt, rounded, as long as eye. Mouth wide, 
slightly oblique ; lower jaws longer, firmly joined; upper short, protractile. 
Teeth conical, hooked, in bands, outer series larger; pharyngeal in the spe- 
cimen dissected, without a shoulder. Eye large, as long as snout, two 
sevenths of head, little, if any, more than half of forehead. Dorsal large, 
base as long as head, or longer than its distance from the head, low, origi- 
nating in front of mid length and, in the female, little farther forward than 
the anal. Base of anal short, not half as long as that of dorsal. Anal of 
male advanced and modified to form an intromittent organ, one third or 
more of the total length of the fish. Ventrals small. Caudal broad, subtrun- 
cate to convex on hind border. Scales large, on mid flank short and deep. 
Olivaceous to brownish, light to dark, reddish to yellowish, edges of 
scales darker ; belly lighter, white to yellowish, with a metallic lustre. In 
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