EIGENMANN: the freshwater fishes of BRITISH GUIANA 121 



Type, Aspredo filamentosus Cuvier and Valenciennes. 



Distinguished by the marginal tentacles of the head and breast, and by the 

 absence of prominent hooks on the ethmoid. Nasals each with a hook, which 

 is partially concealed. A single pair of mental barbels. 



3. Chamaigenes filamentosus (Cuvier and Valenciennes). 



Aspredo filamentosus Cuvier and Valenciennes, Hist. Nat. Poiss., XV, 1840, 

 437, pi. 450 (Cayenne).— GtJNTHER, Catalogue, V, 1864, 270 (Demerara).— 

 EiGENMANN and EiGENMANN, Proc. U. S. Nat. Mus., XIV, 1891, 26. 



Platystacus filamentosus Eigenmann and Eigenmann, Proc. Cal. Acad. Sci., (2), 



II, 1889, 50; Occasional Papers Cal. Acad. Sci., I, 1890, 24. 

 Chamaigenes filamentosus Eigenmann, Eepts. Princeton Univ. Exp. Patagonia, 



III, 1910, 380. 



Several specimens; largest about 215 mm. Georgetown. (C. M. Cat. No. 

 1553a-e; I. U. Cat. No. 11971.) 



Distance from tip of snout to dorsal plate about 4.5 in the length to base of 

 caudal; depth of head about half its width, which is almost equal to its length 

 to upper angle of gill-openings. A. 51-56; D. 5; last ray adnate for half its length, 

 the first ray extremely elongate, considerably longer than its distance from the 

 tip of the snout in the adult. 



Eye small, about one-fourth the interorbital; maxillary barbel reaching gill- 

 opening or pectoral, scarcely adnate; patches of teeth of the two premaxillaries 

 forming a single band; width of mouth about one-third the width of the head; 

 a small barbel on the maxillary barbel opposite the corner of the mouth; a series 

 of barbels directly back of it past the base of the pectoral; a pair of post-mental 

 barbels, corresponding in position to the post-mentals in tibicen; no mental barbels. 



A round pectoral pore under the tip of the humeral process; pectoral spine 

 with hooks on its inner margin, increasing in size toward the tip; those of the 

 outer margin small, directed at right angles to the spine. 



Chocolate, without blotches; lower surface plain; a dark streak back from eye. 

 Anterior part of anal hyaline; ventrals dusky, other fins blackish. 



AsPREDiNiCHTHYS Blecker. 

 Aspredinichthys Bleeker, Nederl. TSjdschr. Dierk., I, 18G3, 118 (tibicen). 



Type, Aspredo tibicen Temminck. 



Readily distinguished by the four nasal spines and the marginal tentacles of 

 the head and breast. 



