1883.] 



NATURAL SCIENCES OF PHILADELPHIA. 



145 



Leucus olivaceus sp. nov. 



The largest cyprinoid of the Pyramid Lake, and veiy abundant. 

 The shape is a regularly compressed fusiform. The head narrows 

 to the muzzle, and the mouth opens obliquely forwards and 

 upwards. The end of the maxillary bone, when the mouth is 

 closed, is concealed in a sheath, and extends a little beyond the 

 anterior margin of the eye. The latter enters the length of the 

 muzzle (without the chin) 1-33 times; and the interorbital space 

 1*60 times. Middle of front a flat longitudinal surface, bounded 

 on each side by an angle, from which the surface slopes to the 

 superciliary border. In the Myloleucus parovanus, a fish of 

 similar size, the frontal is flat roof-shaped, there being a median 

 longitudinal angle. In specimens from Klamath Lake, however, 

 the lateral angles are more distinct than in those from Goose 

 Lake. This fish is everywhere a dusky olive, except on the belly, 

 which is silvery. No lateral band. Fins dusky. 



MeasureTuents. 



Total length, with caudal fin, . 



Length to edge of opercle, . . • . 



Length to base of dorsal, on lateral line, 



Length to base of ventral, on lateral line, 



Length to base of anal, on lateral line. 



Length to base of caudal, on lateral line. 



Depth at first dorsal ray, . 



Depth at first anal ray. 



Depth at caudal peduncle, . 



Width of interorbital region. 



Width of orbit, 



M. 



•283 

 •064 

 •122 

 •131 



•lt3 

 •235 

 •060 

 •043 

 •027 

 •020 

 •0126 



This and the smaller L. dimidiatus swim in schools in the lake, 

 and may be seen from the elevated road along the rocky shores, 

 rippling the surface like a gust of wind. At this signal, the 

 pelicans, gulls and terns quickly congregate, and are soon actively 

 employed in fishing. 



Leuous dimidiatus Cope. sp. nov. 



This very abundant fish is much smaller than the adult L. 

 olivaceus, and has a more slender form, smaller scales, and a 

 difierent coloration. The eye nearly equals the interorbital width 



