1837.] PIIOCEEDINGS OF UNITED STATES NATIONAL MUSEUM. G31 



DESCRIPTION or A NEW GENUS AND SPECIES OP FISH, ACRO- 

 TUS WILLOUGHBYI, FROM WASHINGTON TERRITORY. 



By TARIiETOlV H. BEAN. 



On the 12tli of July, 1887, Mr. Charles Willougbby, United States 

 Indian Agent at tlie Qainaielt Agency, Wash. Terr., sent to the U. S. Na- 

 tional Mnseum a description and color sketch, ot a fish which was un- 

 known to its captors and to all wiio saw it at the agency. The species 

 was recognized in the Museum as a near ally of Icosteus, but its extra- 

 ordinary size (nearly G feet in length) and the lack of ventrals in the 

 original drawing caused a suspension of judgment as to its relationship 

 until the fish was received in December, 1887, from Mr. Willoughby. 

 It was then observed that the species represents a new and unexpected 

 member of the family including Icosteus and Icichthys. 



Acrotiis, new genus. 



Shape of body as in Icosteus, from whicli it differs in the absence of 

 ventrals and spiny tubercles along the lateral line, and in having an 

 emarginate caudal. 



Head short ; moutl] moderate ', eye small. Teeth minute, uniserial, 

 on intermaxillary and mandible ; vomer, palate, and pharynx toothless. 

 Gill-openings w ide, the membrane not attached to the isthmus. Gills 

 four, a wide slit behind the fourth. Gill-rakers short, soft, and flexible. 

 Pseudobranchiii" well developed. Branchiostegals six. Vent some- 

 what in advance of middle of body. Caudal peduncle very slender. 

 Ventrals absent. Caudal large, emarginate. Skin uaked. Lateral 

 line without tubercles. Bones all soft and flexible. Size large. 



Acrotus willoughbyi, new species. 



The type of the species (catalogue number, 39310) is 63^ inches long. 

 The viscera are w^anting. TLe specimen was obtained at Damon, Wash. 

 Terr., July 9, 1887, by Charles Willoughby. 



The greatest height of the body at the vent is contained three and 

 one-third times in the total without the caudal. The caudal peduncle 

 is very slender; its least height little more than one-third of its length 

 and not much exceeding one-fourth the length of the head. The length 

 of the head is about one-sixth of the total without caudal. The snout 

 forms one-fourth, the eye one-twelfth, and the interorbital width one- 

 third of the length of the head. The maxilla reaches to below the mid- 

 dle of the eye. The upper jaw is one-third as long as the head. Gill- 

 rakers fifteen, of which nine are below the angle; the longest about 

 as long as the eye. 



The origin of the dorsal has not been clearly made out; the first ray 

 that can be seen without dis.section is nearly midway between the eye 



