186 



ON THE ICHTHYOLOGY OF LAKE TITICACA. 



more elongated body and shorter fin bases. The head, according to Glinther, is 

 one-third the length in that fish, and the radii are A. 14-16 ; D. 18-19. It is 

 dedicated to Professor Spencer F. Baird, the assistant secretary of the Smithsonian 

 Institution, the alma mater of many naturalists of the present and coming gene- 

 rations. 



3. Obestias ortonii, Cope, sp. nov. 



Radii of the fins, P. 18; D. 16; A. 16. Dorsal outline gently arched to 

 interorbital region, muzzle horizontal, narrowed, the mouth directed vertically 

 upwards. Length of head one-fourth the total, minus the caudal fin, the greatest 

 depth entering the same three and one-third times. Eye four and a half times in 

 the length of the head, and twice in the interorbital width. Lower limb of preo- 

 percle three-fourths as long as the posterior. Scales of lateral line, beginning 

 above anterior part of operculum, thirty-two. On the anterior part of the body 

 they are thickened and enlarged, there being but eight rows from the base of 

 superior ray of pectoral fin to the median nuchal row. They extend forwards to 

 between the eyes, and cover the entire operculum, preoperculum, and suborbital 

 bones. All are entirely smooth. The dorsal fin is further from the caudal than 

 the length of its base. Preorbital bone deeper than long. 



M. 

 .162 



.133 



" to basis anal fin 



" to operculum . 

 " to preoperculum 

 " to orbit . 

 Depth of head at orbit 



Color silvery, the enlarged scales of the anterior part of the body green; head 

 above black, sides vellow. 



This species appears to be most nearly allied to the Orestias owenii, Cuv. Val, 

 in the proportions of the head to the body, but the head is of a different form. 

 Giinther states that the head of O. owemi is "nearly three-fourths as long as high;" 

 in O. ortonii it is two-thirds as high as long. The caudal peduncle is longer in 

 O. ortonii, and the fin-rays of O. owenii are stated to be D. 14-5 ; A. 13-6. In 

 O.jussicei the body is shorter by one length of the head, and the radii are D. 14 ; 

 A. 15. 



This species is dedicated to Professor James Orton, of Vassar College, the 

 indefatigable explorer of the Peruvian Andes. 



Total length 



Length to basis caudal fin 



.082 

 .033 

 .022 



.008 

 .026 



