222 PROCEEDINGS OF THE ACADEMY OF [Apr., 



Trachycorystes isacanthus (Cope). 



Auchenipterus isacanthus Cope, Proc. Amer. Philos. Soc, XVII, 1878, p. 

 677. Peruvian Amazon. 



Nos. 21,444 and 45, A. N. S. P., cotypes of A. isacanthus Cope. 

 Peruvian Amazon. J. Orton. 



Trachycorystes galeatus (Linnaeus). 



Two examples from Surinam agree with my Rupununi River 

 example in every respect. They also agree with Regan's figure of 

 Pseudauchenipterus guppyi and his description of Par auchenipterus 

 pasecB}^ 



Trachycorystes brevibarbus (Cope). 



Auchenipterus hreviharhus Cope, Proc. Amer. Philos. Soc, XVII, 1878, 

 p. 676. Peruvian Amazon. 



No. 21,519, A. N. ^. p., type of A. hreviharhus Cope. Peruvian 

 Amazon. J. Orton. The ventrals are I, 5, not 7 as stated by Cope. 

 Maxillary barbels not reaching middle of pectoral sphie, but now 

 only to about \ its length (tip broken). This species is close to 

 T. galeatus, but differs in the broader predorsal plate, rougher casque 

 and spines. 

 Pseudauchenipterus nodosus (Bloch). 



Surinam. 

 Epapterus dispilurus Cope. 



Proc. Amer. Pliilos. Soc, XVII, 1878, p. 677. Peruvian Amazon. 



Nos. 21,353 and 54, A. N. S. P., cotypes. Peruvian Amazon. 

 E. D. Cope. 



Auchenipterus nuchalis (Agassiz). 



Peruvian Amazon. 

 Auchenipterus ambyiaous sp. nov. Fig. 6. 



Head 4f ; depth 4i; D. I, 6, i; A. in, 41, i; P. I, 10; V. i, 14; 

 head width H in its length; head depth at occiput If; snout 3; eye 

 3f ; mouth width 3; interorbital 2^; least depth of caudal peduncle 

 2\; pectoral spine 1^; ventral fin IJ; third simple anal ray 2|. 



Body elongate, greatly compressed, contour elongately fusiform 

 with greatest depth about midway in leng-th of head and trunk. 

 Caudal peduncle compressed, least depth 1\ in its length. 



Head small, about wide as high at occiput, profiles similar. Snout 

 broad, convex over surface, length about f its greatest width. Pre- 

 orbital width slightly swollen. Eye large, slightly low, center at 

 first f in head length, and orbit well extended on lower side of head. 



10 Proc. Zool. Soc Londcm, 1906, p. 387. 



