SOUTH AMERICAN NEMATOGNATHI. 223 



plates. Brown, a darker spot behind each median hook. 

 D. I, 6; A. 12; P. I, 7; V. 7; Lat. 1. 31. dentatns 167. 

 hh. A yellow lateral band. 



k. Lateral bands meeting above the eyes. 



I. Humeral process four times as long as high. 



costatus 168. 



II. Humeral process- twice or thrice as long as high; a light 

 line along the back. D. I, 6. armatulus 169. 



kk. Lateral bands not meeting above the eyes. 



m. Lateral scutes high, covering the whole side of body and 

 tail, extending to base of anal, the scutes with numerous 

 longitudinal ridges, each of which ends in a marginal 

 point. Humeral process broader than the pectoral spine. 

 Brown, a lighter lateral band. D. I, 6; A. 9; P. I, 6; V. 7; 

 Lat. 1. 29-33. (Giinther.) hancockii 170. 



mm. Lateral scutes low, except those below dorsal fin which 

 are very high. Dorsal spine as high as half its distance 

 from tip of snout. Pectoral spine flat, striate on sides, 

 reaching to the ventral fins. Eye 8 in the head, more 

 than 2 in the interorbital. Maxillary barbels reaching 

 middle of humeral process, mental barbels half as long. 

 Head flat; dorsal plate steeply roof-shaped. Humeral 

 process striate. Caudal deeply forked. D. I, 6; A. 11; 

 V. 7; P. I, 8; Lat. 1. 40. (Cope.) brachiattis 171. 



dd. Dorsal spine serrate in front, not behind. (ACANTHODORAS.) 

 n. Caudal rounded. 



o. Dorsal spine serrate on anterior margin only; D. I, 5. 



calderonensis 172. 



oo. Dorsal spine serrate on anterior margin and on sides. 

 p. Lateral scutes not meeting above and below on caudal pe- 

 duncle; a light lateral band and a dorsal band. Body broader 

 than deep; depth of the head 1J in its length; eye 5 in the 

 head, 2 in the interorbital; anterior margin of the orbit 

 spiny. Maxillary barbels extending past the base of the 

 pectorals; lower jaw scarcely shorter than the upper; width 

 at angle of mouth l^-lf in the head. Humeral process 

 extending to near the tip of the pectoral spine. Lateral 

 plates with a marginal series of spines. Dorsal spine with 

 a serrate ridge on each side. Head 4J; depth 4^-4^; D. I, 

 4-5; P. I, 4-5; V. 6; A. 9-12; Lat. 1. 25-30 (compiled). 



cataphractus 173. 



pp. Lateral scutes meeting above and below on caudal ped- 

 uncle. A light lateral band, numerous white spots on sides, 

 especially 011 the belly. Dorsal spine with two or three 

 spiniferous ridges on its sides; spines on basal half of 

 caudal fin. xninoxxixxiinn* 174. 



