THE AMERICAN TETRAGONOPTERINAE. 65 



scale with a few widely diverging striae and numerous shorter ones along the 

 margin; anal sheath composed of two series of scales in front, of a single series 

 behind; caudal lobes scaled for about half their length; lateral line not greatly 

 descending, the rows of scales above and below it parallel with it; a well-devel- 

 oped axillary scale. 



Dorsal about equidistant from snout and caudal, short and high, its height 

 3.66 in the length; anal margin nearly straight, but the anterior rays nearly 

 twice as high as the posterior; pectorals reaching ventrals, the latter not to the 

 anal, equidistant from tip of snout and base of last anal ray. 



Brownish above, silvery on the sides; a series of dark lines between the 

 series of scales; a faint humeral spot just above the fourth scale of the lateral 

 line; a large caudal blotch not extending forward or to the end of the middle 

 rays. 



This species can easily be distinguished by its crenate scales, compressed 

 breast, and peculiar coloration. 



It is very probable that Fowler's Astyanax oligolepis is this species. If 

 the rows of scales are as Fowler figures then his specimens are distinct, differ- 

 ing from all other species of the group. 



3. Moenkhausia Eigenmann. 

 For William J. Moenkhaus. 



Moenkhausia Eigenmann, Smithsonian misc. coll. quart., 1903, 45, p. 145. 



Type. — Tetragonopterus xinguensis Steindachner. 



Small fishes differing from Tetragonopterus in the course of the lateral 

 line. The line is straight or but little decurved. In other characters some 

 of the species of this genus agrees with Tetragonopterus. The species differ 

 greatly in shape. The extreme in one direction are very compressed and very 

 deep, the depth being more than one half the length. The extreme in the other 

 direction are quite slender, subspindle shaped, the depth being only one fourth 

 of the length. The preventral area may be either narrowly rounded, as in M. 

 profunda, latissima, comma, and oligolepis, more broadly rounded as in M. 

 chysargyrea, or flat with lateral angles as in M. jamesi, megalops, et al. There 

 is a regular median series of scales in front of the ventrals. The anal rays range 

 from 18-37, in number; the scales from 22-39; the lateral line is complete except 

 as noted under M. australe, cotinho, and sanctae filomenae. In these species the 



