2 SMITPISONIAN MISCELLANEOUS COLLECTIONS VOL. 9I 



much shorter than the upper, which projects considerably in advance 

 of the tip of the mandible. Tongue largely adnate to the floor of the 

 mouth, though the tip and lateral margins are free. Lips undeveloped, 

 the lateral teeth fully exposed when the mouth is closed. Pores of 

 head slitlike, a laterolinear series on both jaws. 



The only other genus in the family Muraenesocidae that this new 

 genus closely resembles may be distinguished from it by the following 

 key : 



I a. Teeth in the jaws in bands which are divided by a longitudinal edentulous 

 groove extending the entire length of the bone. 

 2a. Posterior nostrils subcircular, situated in the midlength of the snout. 



Branchiostegal rays 10 or more Xenoiiiystax. 



2h. Posterior nostrils slitlike, situated about one diameter of the eye in ad- 

 vance of the orbit, or at about the beginning of the posterior third 

 of the snout length. Branchiostegal rays 8 or fewer. . . Paraxenomystax. 



To this new genus I would refer Xcnomystax trucidans Alcock, 

 which is separated from the new species in the following key : 



la. Posterior nostrils slitlike, situated about the diameter of eye in advance 

 of orbit. 

 2a. Gill openings about midway between tip of snout and vent ; origin of 



dorsal fin well in advance of pectoral fin base trucidans. 



2b. Gill openings about half length of head nearer tip of snout than vent ; 

 origin of dorsal fin above or behind base of pectoral fin bidenfatus. 



PARAXENOMYSTAX BIDENTATUS, n. sp. 



Holotypc. — U.S.N.AI. No. 108444 (field No. 545) ; 458 mm. 

 standard length; from Caroline station 96, latitude i8°36'oo" N., 

 longitude 65°05'3o" W., to latitude i8°37'i5" N., longitude 65°03'oo" 

 W., March 3, 1933, otter trawl, 270 to 330 fathoms. 



Parafypc. — U.S.N.M. No. 108445 (field No. 15) ; 354 mm. stand- 

 ard length; from Caroline station i, about 5 miles oiT Punta Boca 

 Juana, latitude i8°33'45" N., longitude 66°i5'oo" W., January 30, 

 1933, otter trawl, 360 to 600 fathoms. 



Body scaleless, covered with very thin delicate skin ; subcylindrical, 

 the caudal portion strongly attenuated posteriorly. Vertical fins well 

 developed and continuous with the caudal fin, which is lanceolate and 

 composed of 6 rays. Pectorals long, narrow, about one-third length 

 of snout, with 9 rays. Snout long, evenly tapering forward, sides of 

 snout ilat and straight, its width at anterior nostrils equal to its length 

 in front of the tubes. 



Tip of snout strongly projecting beyond symphysis of mandible, 

 the preoral length about equal to vertical diameter of eye. Head of 

 vomer entirely preoral and bearing a U-shaped patch of sharp coni- 



