Genus Xenomystax Gilbert 
Xenomystax GILBERT, Proc. U. S. Nat. Kus., vol. 14, 1891, p. 
348. Type Xe nomystax atrarius GILBERT. 
Body long, shorter than long tapering tail. Head rather large. 
Snout long, slender. Eye rather large, little advanced. Mouth cleft 
long, reaches beyond eye midway in head. Teeth conic, slender, sharp, 
mostly de pressible, in broad bands in jaws, upper with edentulous 
groove on maxillary separating 2 parallel lengthwise bands. Vomer 
with teeth. Tongue small, adherent. Front nostril large, subtubular 
slit near snout tip, hind one slit on side of snout nearly medial. 
Gill opening large, interspace narrow. Branchial openings into 
pharynx wide slits. No scales. Vertical fins well developed, con¬ 
fluent, dorsal beginning little before gill opening. Pectoral less 
than snout* 
