268 PROCEEDINGS OF THE NATIONAL MUSEUM vol.94 



7.18 (7.84); longest ray of pectorals 10.2 (9.80); least depth of caudal 

 peduncle 6.66 (6.86); length of caudal peduncle 17.9 (17.6); longest 

 ray of caudal fin 14.9 (16.7); distance from tip of snout to origin of 

 doi-sal fin 7.08 (6.96) ; snout to anal origin 55.9 (64.2) ; snout to pel vies 



45.1 (44.6T. 



The following counts were made: Dorsal rays iii,8 (iii.8) and, in 

 addition, 6 paratypes had iii,8, and 3, iii,9 rays; anal rays iii,lS (iii,20), 

 in addition one paratype had iii, 18, 2, iii,19, 3, iii,20, and 2, iii,21 anal 

 rays; pectoral rays i,5 (i,5) and i,5 in 9 other examples coimted; pelvic 

 rays always i,4; branched caudal fin rays always 11, with 5 above and 

 6 below. 



The head is greatly depressed forward, the body becoming rounded 

 opposite pectoral fins and much compressed from pelvic fins posteri- 

 orly; the greatest depth occurs between pel vies and anal origin; the 

 greatest width is across the eyes; mouth inferior but lower lip not 

 reverted except at corner of mouth; a single maxillary barbel not 

 reaching past pupil; margin of eyes not free; pupil round; gill mem- 

 branes jomed across isthmus with wide free fold; pectorals reaching 

 about one-third the way to pelvics; pelvics short, the distance between 

 pelvic insertion and anal origin about 6 times in standard length; 

 pelvics inserted closer to tip of snout than to base of caudal fin by 2 eye 

 diameters; anal origin about 1% eye diameters in front of a vertical 

 line through dorsal origin; first rays of anal longest, tapering to shorter 

 rays posteriorly; caudal fin concave; nostrils widely separated, con- 

 nected by a tube, the anterior nostril with a raised rim, posterior 

 opening covered by a valvular flap; anus immediately in front of anal 

 origin. 



Color (in alcohol).— White, eyes black; a series of black pigment cells 

 along bases of dorsal and anal fins, and a line of larger black pigment 

 cells extends from below and behind pectoral fins to anal origin ; caudal 

 fin slightly dusky posteriorly, other fins translucent. No pigment 

 spots on top of the head. 



Remarks. — This new species may be distinguished from all other 

 members in the subfamily Tridentinae by means of the keys on page 

 266 and below. 



The following key gives the main differences between Tridensimilis 

 venezuelae and T. brevis, which I believe should be referred to this new 

 genus until such time as additional specimens of brevis are collected 

 and then its true nature determined. Perhaps then on the basis of 

 two maxillary barbels brevis should be made the type of still another 

 genus. 



la. A single maxillary barbel present at an.de of mouth not extending past pupil; 

 distance of origin of dorsal 2^ in total length; distance of anal origin from 

 tip of caudal 2)-i to 2^ in total length; first pectoral ray not produced; no 

 pigment spots on head Tridensimilis venezuelae, new species 



