434 CALIFORNIA ACADEMY OF SCIENCES. 



Dorsal fin as long as its distance from tip of snout, its 

 height greater than its length in the young, its height 

 scarcely more than half its length in the adult. 



Caudal in the adult short, the rays provided with bris- 

 tles; in the young the caudal is long, the lowermost ray 

 being 2 in the length. 



Pectoral spine bristly, reaching past base of ventrals, 

 these reaching past base of anal in the young, the ven- 

 trals not reaching the anal in the very old. 



Dark brown, everywhere marked with yellow or dirty 

 white, the light color on the head forming irregular bars 

 and spots which are radially arranged on the occiput, 

 sometimes forming two stellate spots between the eyes; 

 each lateral scute on the tail with a short, median bar of 

 light, on the abdominal portion with irregular light 

 spots; ventral surface with vermiculating light bars; fins 

 all dark brown with light spots on the rays. 



Head 3; D. I, 12-13; A. I, 4; Lat. 1. 29. 



Thirteen specimens .15-. 41 m. Rio Preto; Rio Puty; 

 Sao Gongallo; Xingu Cascade. The specimen from 

 Xingu is more uniform black and has the fins more 

 greatly developed. 



LXXXIX. PSEUDANCISTRUS. 



Hypostomus Cuv. & Val. Hist. Nat. Poiss. xv, 1840 (sp.) 



Pseudancistrus Bleeker, Nederl. Tijdschr. Dierk. i, 

 1863, 77 (barbatus). 



Plecostomus Giinther, Cat. Fish. Brit. Mus. v, 237, 

 1864 (sp.) 



Type: Hypostomus barbatus Cuv. & Val. 



Habitat: Rio Mucuri; Guiana and Colombia. 



This genus is closely allied to Plecostomus and to />//>- 

 osarcus, but differs from both in having the head mar- 

 gined with bristles. This not a sexual character in Ps. 

 wertheimeri; whether it is or is not in the other species we 

 are unable to say. The lower surface of the tail normal 



