240 MEMOIRS OF THE CARNEGIE MUSEUM 



Choetostomus leucostidus Gunther, Catalogue, V, 1864, 248 (Essequibo). — Stein- 



DACHNER. "Flussfische Siidamerika's," iv, 1882, 7 (Rio Huallaga). 

 Ancistrus leucostidus Eigenmann and Eigenmann, Proc. Cal. Acad. Sci., I, 1890, 



447 (Coary; Tabatinga; Jutahy); Proc. U. S. Nat. Mus., XIV, 1891, 43. 

 Chcetosto?nus alga Cope, Proc. Acad. Nat. Sci. Phila., 1871, 287, pi. 15, fig. 3 (Am- 



byiacu). 

 Chaetosiomus malacops Cope, Proc. Acad. Nat. Sci. Phila., 1871, 287, pi. 5, fig. 2 



(Ambyiacu). — Eigenmann and Eigenmann, Proc. Cal. Acad. Sci., (2), II. 



1889, 46; Occasional Papers Cal. Acad. Sci., I, 1890, 443; Proc. U. S. Nat. 



Mus., XIV, 1891, 43. 

 Chcetosiomus tedirostris Cope, Proc. Acad. Nat. Sci. Phila., 1871, 288, pi. 15, fig. 2 



(Ambj'iacu). — Eigenmann and Eigenmann, Proc. Cal. Acad. Sci., (2), II, 



1889, 40; Occasional Papers Cal. Acad. Sci., I, 1890, 442; Proc. U. S. Nat. 



Mus., XIV, 1891, 43. 



One specimen, 63 mm. Gluck Island. (C. M. Cat. No. 1517.) 



Nine specimens, 50-108 mm. Packeoo Falls, Essequibo. (C. M. Cat. No. 

 1518a-c; I. U. Cat. No. 11944.) 



Eighteen specimens, 63-119 mm. Rupununi Pan. (C. M. Cat. No. 1519a-d; 

 I. U. Cat. No. 11945.) 



Head 2.8; depth at tip of occipital 5-5.2 in the length; width of head an 

 orbital diameter or less than an orbital diameter smaller than its length ; interorbital 

 2.25 in the length of the head; mandibular ramus 2.75-3.75 in the interorbital; 

 D. 1,7; A. 1,4; eye 5-6 in the head. About nine interopercular spines, hooked at 

 the tip, the longest in the largest specimen 2.66 in the interorbital. 



Tentacles rather small, the naked area in the largest male with four bifid 

 tentacles; naked area extending one-fourth the distance to the posterior margin 

 of the eye; seven plates between the dorsals, eleven between the anal fin and the 

 caudal plates, and twenty-five along the sides. Last dorsal ray reaching to, or 

 beyond, origin of spine of the adipose; base of the dorsal equal to the distance 

 from the base of the last ray to the tip of the spine of the adipose; dorsal spine 

 equal to snout and orbit; lower caudal ray much longer than the upper, equal 

 to the length of the head. Ventrals rounded, reaching the middle of the anal; 

 pectoral spine reaching the third fifth of the ventrals. 



Black, with a few minute white spots everywhere; dorsal and caudal scarcely 

 or not margined with lighter. 



