148 THE CYPRINODONTS. 



The shape of the head, massive snout, large mouth, numerous teeth, and 

 larger scales readily distinguish this species from its nearest ally 0. Pentlandii. 

 Common in Lake Titicaca. 



Orestias Pentlandii- 



Oreslias Pentlandii Nal., 1839, L'Inst., VII, 118, — 18i6, C. V. Poiss., XVIII, 230, pi. 533; Blkr., 

 1860, Ind. Cypr., 487 ; Gthr., 1866, Cat., VI, 329 ; Cope, 1875, Jour. PhU. Ac, 185 ; Garm., 1876, BuU. 

 M. C. Z., Ill, 275 ; Eig., 1891, P. U. S. Mus., XIV, 65,-1894, Ann. N. Y. Ac, VII, 629. 



Orestias Bairdii Cope, 1875, J. PbU. Ac, 185 ; Eig., 1S93, P. U. S. Mus., XVI, 54. 



B. 5 (rarely 6) ; D. 13-15 ; A. 15-18 ; P. 19-20 ; LI. 55-63 ; Ltr. 15-18; 

 Vert. 16 + 21 or 17 + 20. 



Body elongate, moderately compressed ; caudal pedicel slender, broaden- 

 ing at base of fin. Head one fourth of the length, without the caudal, broad 

 and convex on the crown, narrowing toward the snout. Snout medium, little 

 longer than the eye, rounded, blunt ; chin vertical. Mouth medium, not 

 reaching downward to the level of the lower edge of the orbit, nearly verti- 

 cal. Teeth few, lacking the band of smaller ones behind the outer row, 

 easily lost. Eye shorter than snout, two-elevenths of head, four-ninths of 

 interorbital space. Origin of dorsal half way from occiput to caudal, little 

 forward of that of anal, fin rounded above, forming an angle in the posterior 

 rays. Pectorals moderately broad, reaching two fifths of the distance to the 

 anal. Caudal three fifths the length of head, hinder margin slightly con- 

 cave. Scales thin, somewhat deciduous, one to three vertebral rows larger, 

 about twenty seven from head to dorsal, with age becoming thickened and 

 rugose or smooth on head and shoulders and to some extent backward 

 along the flanks, the hard enlarged series occasionally extending quite to the 

 base of the tail. Belly naked, as also an area along the sides of the anal and 

 behind it, or another at each side of the vertebral series of scales. 



Back brownish, sides lighter to silvery, in lower half, ventral surface 

 white. Young mottled and blotched on the back. Dorsal and caudal brown- 

 ish, with or without small spots of brown, that sometimes form transverse 

 series. Fins in cases brownish toward the outer edges. Pectorals bi'ownish 

 in upper half, white in lower. Very common in Lake Titicaca. Specimens 

 from the Cuzco Valley are about two thirds as large as those described ; they 

 are much darker on the back, above the lateral line, and apparently belong 

 to a distinct variety, fusctis. 



