SOUTH AMERICAN NEMATOGNATHI. 447 



439. Ancistrus leucostictus. 



Chcetostomus leucostictus Giinther, v, 248, 1864 (Essequibo); Stein- 

 dachner, FlussfischeSiidamerika's, iv, 7, 1882 (Rio Huallaga). 



Ancistrus leucostictus Eigenm. & Eigenm. Proc. Cal. Acad. 2d Ser. 

 ii, 48, 1889 (Coary; Tabatinga; Jutahy). 



Chcetostomus alga Cope, Proc. Acad. Nat. Sci. Philad. 1871, 287, pi. 

 15, tig. 3 (Ambyiacu Kiver). 



Habitat: Coary to the Huallaga. 



Short, depressed; the depth about 1-f in the width. 

 Head broad flattish; the surface of its shields granular; 

 the temporal shields more coarsely granular, striate. 

 Occipital plate margined by three nuchal plates behind. 

 Postfrontal plate forming the postero-superior two- 

 fifths of the orbit, a suborbital forming postero-in- 

 ferior fifth; the temporal plate entirely separate from 

 the orbit. Interorbital broad, flattish. Transverse pro- 

 file of the snout convex. Snout, in the male, broadly 

 naked with numerous simple and few bifid or trifid 

 tentacles; in the female, narrowly naked with a mar- 

 ginal series of simple tentacles. 



Orbit 3-4J in the snout, 5J-7J in the head, 3-4 in 

 the interorbital. 



Opercle and preopercle erectile; opercle with a mar- 

 ginal series of fixed spines; preopercle with from 9 to 

 12 erectile spines, the longest equal to 2 orbital diame- 

 ters. 



Maxillary barbels short; teeth very fine. 



Ventral surface naked except a minute granular plate 

 below the pectoral spine. 



All the scutes with serrate ridges ending in marginal 

 spines; no keels. 



Distance of dorsal from tip of snout 2-J- in the length; 

 base of dorsal equals its distance from the caudal. 



Caudal obliquely emarginate, the outer rays prolonged, 

 the lower longest. 



Pectoral spine reaching beyond base of ventral. 



Light or dark brown, everywhere with white dots; a 



