682 ZOOLOGY— FISHES. 



ISOPONDYLI. 



COREGONUS, Cuv. 

 COREGONUS VILLIAMSONI1, Gir. 



Coregonus icilliamsonii, Gir., P. R. R. Rep., x, 1859, 320. — Id., Proc. Acad. Nat. Sci. 



Pbila., viii, 1S5C, 136. 

 Coregonus villiamsoni, Cope, U. S. Geol Surv. Wyoming, 1870, 433 — 1(3., U. S. Geol. 



Surv. Montana, 1871, p. 469.— Id, Proc. Am. Phil. Soc. Phila., 1874, 132.— 



Id, Rep. Plagop. & Ichthy. Utah, 1874, 



Specific characters. — Head contained five times and a half in the total 

 length. Month small ; posterior extremity of maxillar bone not extending 

 quite as far as the anterior rim of the orbit. Eye moderate, subcircular ; 

 its diameter entering about five times in the length of the side of the head. 

 Anterior margin of dorsal fin nearer the posterior edge of the base of the 

 adipose than the extremity of the snout. Scales well developed, disposed 

 upon eighteen longitudinal series across the line of the greatest depth ; nine 

 between the lateral line and the base of the dorsal ; and eight between the 

 lateral line and the insertion of the ventrals. Color bluish-lead above, 

 whitish beneath, with a silvery reflect. 



Br. VII : VII ; D. 2, 12 + 1 ; A. 2, 12 + 1 ; C. 5, 1, 9, 8, 1, 6 ; V. 12 ; 

 P. 1G. 



Upon comparison of specimen No. L with Girard's description and type, 

 we find some marked differences, which are here noted. Total length of 

 specimen examined, 17 inches ; but we have seen others even longer. Girard 

 mentions 1 1 inches as the length of his specimen. Head contained nearly 5 J 

 times in the total length. Mouth small ; posterior extremity of maxillar bone 

 extending as fax as anterior rim of orbit. Eye moderate, subcircular ; diam- 

 eter in alcoholic specimen thirteen twenty-fifths of an inch, entering about 

 six times in the length of the side of the head. Anterior margin of dorsal 

 fin nearer the posterior edge of the base of the adipose than the. extremity 

 of the snout. Scales well developed, somewhat larger in dorsal than ven- 

 tral region, disposed upon 20 longitudinal series across the line of the 

 greatest depth just in front of anterior base of dorsal fin, 10 between the lat- 

 eral line and insertion of the ventrals, 10 between the lateral line and base 



