SOUTH AMERICAN NEMATOGNATHI. 295 



ANALYSIS OF THE SPECIES OF AUCHEXIPTERUS. 



a. Humeral process covered with skin; ventrals reaching the anal; A. 

 42-49. 



b. Mental and postmental barbels reaching little beyond middle of pec- 

 torals. Distance of dorsal fin from snout 4-4^ in the length; tip of 

 ventrals reaching 2d or 3d anal ray; pectoral spine not reaching the 

 ventrals, !-! in head. nuchalis 232. 



bb. Mental barbels reaching middle of ventrals, postmentals not to mid- 

 dle of pectorals. Distance of dorsal from snout about 3J in the 

 length; tip of ventrals reaching 8th or 9th anal ray; pectoral spine 1 

 in head, reaching beyond base of ventral fins. fordicei 233. 



aa. Humeral process naked; veutrals not reaching the anal. A. 37. Eye 

 Sin head, interocular space If in head. Dorsal spine 1 in head, 

 weakly serrated behind, smooth in front. Pectoral spine strongly ser- 

 rate behind, smooth in front, as long as the head, not reaching the 

 ventrals. Maxillary barbels reaching tip of pectoral spine, mentals to 

 its base. Head 4f ; depth above first anal ray, 6; D. I, 7; A. 37; V. 14. 

 (Cope.) brachyurus 234. 



232. Auchenipterus nuchalis, 



Hypophthalmus nuchalis Spix, Gen. et Spec, Pise. Bras. 17, pi. 17, 



1829 (Brazil). 

 Auchenipterus nuchalis Cuv. & Val. Hist. Nat. Poiss. xv, 207, 1840; 



Castelnau, Anim. 1'Amer. du Sud, 47, 1855 (Amazon); Kner, 



SB. Ak. Wien, xxvi, 422, 1857; Eigenm. & Eigenm. Proc. Cal. 



Acad. 2d Ser. vol. i, 151, 1888 (Villa Bella). 

 Euanemus nuchalis Giinther, Cat. Fish. Brit. Mus. v, 193, 1864 



(KiverCapin, Para); Cope, Proc. Am. Philos. Soc. xvii, 676, 1878 



(Peruvian Amazon); Vaillant, Bull. Soc. Philom. Ser. 7, iv, 1880 



(Calderon). 



Auchenipterus dentatus Cuv. & Val. 1. c., 210 (Cayenne). 

 Evanemus colymbetes Miiller & Troschel, Horas Ichthyol. iii, 11, pi. 



i, fig. 2, 1849 (Surinam). 

 Habitat: Amazons; Surinam. 



The description of colymbetes agrees with our speci- 

 mens of nuchalis. The plate, however, is somewhat 

 askew, not agreeing with the description. 



Elongate compressed. Head short, its greatest width 

 equal to snout plus the eye; at the base of the occipital 

 process the depth equals the width; head entirely cov- 

 ered with thin skin; dorsal plate deeply emarginate in 

 front and behind, less so on sides, its length on a 

 median line 5 in the diameter of the eye. 



