738 EEPOET OF COMMISSIONER OF FISH AND FISHERIES. 



to edge of occiput, the width of opercuhim, the distances from snout to the 

 insertion of the fins, excepting the dorsal, the lengths of the bases of 

 the lius, the number of rays, the number of branchiostegals, the num- 

 ber of scales in the lateral line, and the number of transverse rows of 

 scales above and below the lateral line, and the number of crecal appen- 

 dages, agree quite closely in a comparison of these species. 



From a comparison of notes furnished by Assistant Surgeon Oldmixon, 

 made from a fresh specimen in Montana, with my own notes, made on the 

 banks of the Ausable River, from fresh specimens from its waters, the 

 coloration is found to differ somewhat. / 



Dr. Oldmixon says that the "red spots "npon the dorsal are " encircled 

 by a thin border of bright emerald-green." The presence of green upon 

 the ventrals, and the fact that the caudal is "plain" as to color, are all 

 points of difference in examining the coloration. 



These variations of characters found to exist in the graylings of dif- 

 ferent regions of i>rorth America warrant the recognition of three species 

 at least, the descriptions of which are given in the following pages. 



The probability of the existence of a grayling in Canada and the 

 Northeastern United States, already referred to, involves the possibility 

 that Yalenciennes' T. ontariensis may again be found, which will at least 

 be likely to revise the nomenclature of the species. 



Thymallus Cuvier. 



Fusiform. Mouth small, with small, needle-like teeth of uniform 



size ; none on the pterygoid bones. Dorsal fin very largely developed ; 



rays of anterior portion of fin simple j posterior rays bifurcated, and often 



unusually prolonged. Thoracic region with minute scales; sometimes 



naked. 



Thymallus signifer Eichardson. 



Coregonus signifer Eichardson, Nar. of Jour, to Polar Sea, Franklin, 



p. 711, pi. 26. 

 Coregonus fhymalloidcs Eich., oj). cit, p. 714, [young.] 

 Salmo {Thymallus) signifer Eich., Bafck's grayling, Faun. Bor. Amer., 



part iii, p. 190, pi. 88. 

 Salmo {Thymallus) thymalloides Eich., lesser grayling, oj). cit., p. 194. 

 Thymalus signifer Cuv. and Val., vol. xxi, p. 450 ; Gliuth. Cat. Fishes, 



Brit. Mus., vi, p 202. 

 Thymalis Pallasii, Dall, Alaska and its Eesources, p. 579 ; Eept. Dept. 



Agric, [U. S.,] 1870, p. 



The greatest height of body is more than the length of the head and 

 much less than the base of the dorsal. The length of the snout is equal 

 to the diameter of the orbit, and less than the interorbital area; the di- 

 ameter of the orbit is equal to the length of the operculum. The ante- 

 rior ray of the dorsal fin is in front of a point midway between the pec- 

 torals and the ventrals. The last ray of the anal fin is posterior to the 

 insertion of the adipose fin. 



The height is 21? hundredths of the length. The distance from the 



