EIGENMANN: the freshwater fishes of BRITISH GUIANA 203 



Cotypes, twenty specimens, 50-73 mm. Tumatumari. (C. M. Cat. No. 1716 

 a-d; I. U. Cat. No. 12108.) 



These specimens differ from demerarce notably in one observed particular: the 

 mandibular barbels extend to about the lower angle of the gill-opening, not to the 

 pectoral. 



The maxillary barbels are as long as in demerarm; depth 5.33. 



Subfamily Ageneiosin^. 

 Tympanopleura'' gen. nov. 



Type, Tympanopleura piperata sp. nov. 



Maxillary barbels only, short. Air-bladder projecting into the abdominal 

 cavity, naked laterally, the skin over it forming a large pseudo-tympanum; snout 

 short, about equal to the eye; profile very concave; first dorsal and first pectoral 

 rays pungent; origin of anal equidistant from rictus and middle caudal rays. 



74. Tympanopleura piperata sp. nov. (Plate XX, fig. 3.) 



Tjrpe, a male, 64 mm. Crab Falls. (Carnegie Museum Catalog of Fishes 

 No. 1708.) 



Cotypes, two males and five females, 57 -61 mm. Crab Falls. (C. M. Cat. No. 

 1709fl; I. U. Cat. No. 12090.) 



This is evidently a young fish. To what extent the large, protruding air- 

 bladder and the large pseudo-tympanum are characters of immaturity I am unable 

 to say. The short snout very i)robably is due to the age of the specimen. 



Head 4.5; depth 4.75; D. 1,5 or 6; A. 31; V. 7; P. 1,9; Br. 7; eye 1 in snout, 

 2.8 in head, 1 in space between the eyes below. 



Profile much concave; fontanel open in front, continued as a groove to above 

 the posterior margin of the pupil; snout rounded, the gape short; maxillary barbel 

 in the male with an osseous base extending to below the anterior margin of the eye, 

 the fleshy tip a little farther; in the female, minute, fleshy, reaching the rictus; 

 gill-opening extending to below the posterior margin of the eye; dorsal spine with 

 minute teeth on its front margin, its posterior margin smooth in the male, with 

 recurved teeth along its entire length in the female; pectoral spine smooth in front, 

 with recurved teeth along its entire margin behind; a large pectoral pore. Distance 

 of dorsal from snout 3.66 in the length; origin of anal equidistant from rictus 

 and caudal; ventrals reaching past origin of anal; pectorals not to ventrals. 



19 rvfiTrafov, tympanum, wXevpa, side. 



