DESCRIPTION OF HYMENOCEPHALUS TENUIS, A NEW 

 MACRUROID FISH FROM THE HAWAIIAN ISLANDS. 



By Charles H. Gilbert and Carl L. Hubbs, 



Of Stanford University, California. 



During the course of their studies on the macruroid fishes of the 

 Japanese and PhiUppine faunas, the authors have reexamined several 

 of the Hawaiian species of tliis group, resulting in the discovery of 

 an undescribed species of HymenocepJialus, widely different from any 

 of the described forms. The description of this new species forms 

 the basis of the present paper. 



HYMENOCEPHALUS TENUIS, new species. 



Hyinenocephalus striatulus Gilbert, Bull. U. S. Fish Comm., 1903 (1905), sec. 2, 

 p. 665 (in part, including only the specimen from Station 3920). 



Type-specimen.— 75 mm. long to end of tail, 20 ram, long to anus; 

 dredged off the southern coast of Oahu, one of the Hawaiian Islands, 

 at Albatross station 3920; depth, 265 to 280 fathoms; bottom tem- 

 perature, 44.6 Fahr.; Cat. No. 78177, U.S.N.M. 



In its form this species differs from all others, being the only one 

 in which the head is not compressed. The width of the cylindrical 

 head is half its length and is just equal to its greatest depth, which 

 is also the greatest depth of the body. Preocular length of snout, 

 1.3 in orbit, 3.6 in length of head. The length of the orbit is a 

 little greater than its vertical height, and is contained 3..15 times 

 in the postorbital, or 2.65 times in the entire length of the head. 

 The hinder margin of the pupil is equidistant from the tip of the 

 snout and from the end of the opercle. The sides of the inter- 

 orbital area are strongly concave; its least width is contained 6 

 times in the head; the least suborbital width is about 0.3 the orbital 

 length. The barbel' is not quite half the length of the orbit. The 

 upper jaw extends from below the front of the nasal fossa back- 

 wards and shghtly downwards almost to below the hinder margin 

 of the orbit. Length of upper jaw 2,25 in that of head. The gill- 

 rakers are tubercular and are fewer in number than in any other 



Proceedings U. S. National Museum, Vol. 54— No. 2231 . 



173 



