THE AMERICAN TETRAGONOPTERINAE. 181 
5. HYPHESSOBRYCON SERPAE Durbin. 
Plate 25, fig. 1; Plate 79, fig. 12, 12a, 12b. 
Hyphessobrycon serpae Durnin, Bull. M. C. Z., 1908, 62, p. 100 (Serpa); Ercenmann, Rept. Princeton 
univ. exped. Patagonia, 1910, 3, p. 436; Exxis, Ann. Carnegie mus., 1911, 8, p. 159. 
Hasitat.— Amazon, Rio Guaporé, Upper Paraguay. 
Specimens examined. 
Number of 
Catalogue number specimens Size in mm. Locality Collector 
20985 Cotypes 46 26-30 Serpa Thayer 
3086 C. 2 27-42 Maciél, Rio Guaporé Haseman 
3087 C. 1 23 Caceres Haseman 
Head 3.5; depth 2.75-3; D.10 or 11; A. 25-30; scales 5-29 to 31-3.5: 
eye 2.5-2.75; interorbital 3 in head. 
Body compressed, deepest at the origin of the dorsal. Depth of head at 
the base of the occipital process 1.5 in the greatest depth. Preventral region 
rounded in front, flattish near the ventrals, without a regular series of median 
scales. Predorsal region rounded, very slightly if at all keeled, with a median 
series of 10 scales. 
Occipital process 5 in the distance from its base to the origin of the dorsal, 
bordered by 3-83.67 scales. Interorbital slightly convex. Frontal fontanel 
narrowly triangular, 1.25 in the much wider parietal, without the occipital 
groove. Second suborbital in contact with the preopercle below, a narrow 
naked border behind it, second suborbital narrow. Mouth moderately large. 
Maxillary almost equal to the length of the eye. Mandible a very little longer 
than the eye. Snout short. Premaxillary with two or three tricuspid teeth 
in an outer row and five to seven 3- to 4-pointed ones in the inner row. 
Maxillary with two, sometimes three, small tricuspid teeth. Dentary with a 
graduated series of five 3- to 5-pointed and five or six minute conical teeth 
on the side. 
Gill-rakers 7 + 16. 
Anal sheath short, consisting of 4 or 5 scales covering the bases of the 
first 8 or 9 anal rays. Pores on 5 or 6 scales of the lateral line. 
Origin of dorsal half the width of the eye nearer to the snout than to the 
base of the caudal, penultimate ray half as long as the longest which is 4 in the 
