NATURAL SCIENCES OP PHILADELPHIA. 93 



dal ; the head three and a half times. The eyes are large, the diameter being 

 contained only three and a half times in the length of the head. The supra- 

 maxillary ends under the posterior border of the pupil. The surface of the 

 intermaxillary has four larger equidistant conical teeth, directed forwards, 

 and a smaller one on each side and farther back, between the external and 

 internal ; the surface of the mandible has also four conical processes. The 

 dorsal commences nearly over the anus ; its height at least equals three fourths 

 of the head's length.* The anal commences nearly under the third dorsal 

 ray. The pectorals extend beyond the anus, and the ventrals, which are 

 inserted nearly midway between the axils of the pectorals and the origin of 

 the anal, extend to about the third ray of the latter. 



The scapular spot is very distinct ; the caudal indistinct. The fins, espe- 

 cially the pectorals, minutely punctuated between the rays. 



I dedicate this specimen to Mr. Philip V. Myers, a travelling companion of 

 Prof. Orton. in compliance with a request of the latter gentleman. 



Hydrolycus Copei, Gill. 



D. 11. A. 43. 



The height enters 2| times in the length (exclusive of the caudal), the length 

 of the head 3J; the profile between the nape and convex snout is moderately 

 incurved ; the interorbital space is slightly arched, and about equal to the 

 orbit, the snout, and a quarter of the head's length. The maxillary passes 

 considerably behind the vertical of the posterior border of the orbit. The 

 dorsal fin commences above the anus. The pectorals pass for a third of their 

 own length beyond the axillae of the ventrals, and the ventrals extend back- 

 wards to the third or fourth anal ray. 



The lateral spot is faint, and above the lateral line, just in advance of the 

 vertical of the anus. 



Four specimens, the largest of which is four and a quarter inches long, 

 were obtained in the Napo and Maranon rivers. 



I dedicate this species to my esteemed friend, Prof. Cope, in recognition of 

 his important contributions to herpetology and ichthyology. 



Subfamily SERRASALMONIN.E. 



Pygocentrus altus Gill. 



P. 17. V. 7. D. 17. A. 33. 



The height of the body is contained about 3 4-5ths in the length, exclusive 

 of the caudal ; the length of the head (measured from the prominent lower 

 jaw) about 2f. The back declines very slowly towards the nape ot the neck, 

 and thence is boldly decurved downwards. Snout obtuse, less than the diam- 

 eter of the eye. The diameter of the eye equals a fifth of the head's length, 

 and the interorbital width enters 2 in the same distance. The second sub- 

 orbital bone is separated from the preoperculum by a lunate naked area. 

 There are fourteen teeth in each jaw. The origin of the dorsal fin is nearer 

 the eye than the root of the caudal; its height is less than half the heads 

 length. The origin of the anal is under the last dorsal rays Ihe pectorals 

 scarcelv reach the bases of the ventrals ; the latter are two thirds as long as the 

 former' Gill-rakers of the outer branchial arch short and pointed like those 

 of the other arches. Abdomen armed with about twenty-seven serratures. 



The color is greyish, iridescent, and tinged with bhie.sh ; here is no well 

 defined scapular spot, but the region above the operculum is darker 



Nearly related to P. scapular is (Serrasalmo scapulans Gthr. v. p. dbaj. 



* The anterior dorsal rays are broken. 



1870.] 7 



