THE CYPRINODONTS. 57 
This description applies fairly well to the teeth of our specimens of 
P. unimaculata, The greatest deviation appears in the outer series on the 
jaws, which teeth are not conical in adults (Plate V. Fig. 7), though in very 
young ones there is sufficient approach to that shape to justify the statements 
made. 
Peters, 1864, suggested the identity of vivipara and surinamensis. Gthr., 
1866, united them. Steindacher, 1881, after examining specimens of uni- 
maculata from Rio Janeiro, Parahyba, Surinam, and Cayenne, remarks : 
“Vielleicht ist P. surinamensis Val. von P. unimaculata Val. der Art nach 
nicht verschieden.” Numerous representatives, from Rio Janeiro, Porto 
Seguro, Bahia, Pernambuco, Parahyba, a number of points on the Amazon, and 
from British Guiana, make it reasonably certain that Valenciennes species 
are identical. The figure given by Bloch and Schneider is quite mislead- 
ing. Peters in his study of the type found the fork in the tail to be due to 
accidental mutilation, and the bands he traced to loss of scales. As shown in 
the description many individuals are yellowish, hardly so bright as the figure, 
and transverse bands, not distributed quite as in the figure, are of the com- 
monest marks in the specimens of unimaculata Val. The figures in the for- 
mula originally given for vivipara, are, excepting the number of ventral rays, 
generally conceded to represent variations of one or two each from the actual 
averages, 
Pecilia dominicensis. 
Plate IV, Fig. 12, teeth, 
Pacilia dominicensis Val., 1846, C. V. Poiss., XVIII, 131, pl. 526, fig.1; Blk., 1860, Cypr., 486; Gth., 
1866, Cat., V1, 346; Jor., 1887, P. U. S. Mus., IX, 564. 
Pacilia melanogaster Gth., 1866, Cat., VI, 345; Jor., 1887, P. U. S. Mus., IX, 564. 
Peacilia (Acropecilia) tridens Hilg., 1889, Sb. Ges. Nat. Fr., 52. 
B. 5-6; D.9-8; A.10-9; V.6; P.15; Li. 26-28; Ltr. 8; Vert. 
14 + 15. 
Body rather short and stout, compressed, caudal pedicel deep ; depressed 
on nape and head. Head broad, flattened on the crown, two sevenths of the 
length to the base of the caudal, less than depth of body. Snout short, about 
half the length of the orbit, subtruncate ; chin short, steep. Mouth as wide 
as the eye, opening upward ; lower jaws weak, loosely joined, longer than 
upper; upper shorter, protractile. Teeth in outer series slender, narrow at 
the bases, broadened toward the apices, hooked ; inner teeth small, in a vili- 
form band, tricuspid ; pharyngeal slender, hooked, with a shoulder, arranged 
