144 



PROCEEDINGS OF THE ACADEMY OF 



[1883. 



of Girard, but he gives the scale formula of that species as 

 8-50-5, and the anal rays as 7 — characters quite inconsistent with 

 the M. parovanus. 



Myloleucus thalassinus sp. nov. 



This species rests on a single specimen which I obtained at 

 Goose Lake, Oregon. It is a more slender fish than the M. paro- 

 vanus^ and its color when fresh is light, translucent green, quite 

 different from the more or less heavy olivaceous color of the 

 latter. Its proportions are expressed in the key above given, as 

 well as the smaller number of longitudinal rows of scales, and 

 the additional ray of the anal fin. 



Measurements. 



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 ra,y^ 



Depth of caudal peduncle. 



Width of interorbital region, . 



Width of orbit, .... 



LEUCTIS Heckel. 



M. 



•143 



•031 



•059 



•061 



•0805 



•114 



•026 



•022 



•014 



•010 



•OOt 



Fische Syriens, 1843, p. 48. Anchi/lopsis Cope, Proceed. Amer. Philos. Society, 1870, 

 p. 543. 



I found recent species of this genus in Pyramid Lake, Nevada, 

 only. Some extinct species occur in the pliocene beds of Oregon 

 and Idaho. ^ The two species from P3'ramid Lake differ as follows : 



Scales 18-14—56-9—7-8; anal rays I. 8; head 3-66 in length; depth 

 4 (3-75); eye in head 5 times. L. olivaceus. 



Scales 14-15 — 63-6 — 8 ; anal rays I. 8 ; head 4 times in length ; 

 depth 4-5 times ; eye 3'5 in head. L. dimidiatus. 



^ Leucus latus; Anchybopsis latus Cope, Proceeds. Amer. Philos. Soc, 

 1. c, Idaho; size large. Leucus altareus; Anchybopsis altar.cus Cope, loc. 

 cit., 1877, p. 239. From Oregon; small. 



