184 NORTHERN ZOOLOGY. 



nues usually taken in the nets vary in weight from five to fifteen pounds, but indivi- 

 duals are reported to have been caught of thirty or forty pounds. 



The Inconnu differs from the typical trouts in its general aspect, and in the small- 

 ness of its teeth, which are crowded like velvet pile, and are altogether wanting 

 on the labials : it seems to stand on the confines of the sub-genus, and to connect 

 the truttce with the coregoni. It disagrees with the latter in the number of its 

 gill-rays, in having palatine and vomerine teeth, and in the form of the body. 



DESCRIPTION 

 Of a specimen taken in Great Slave Lake in the spring of 1822. 



Colour of the back and sides changing from bluish-grey to greenish-grey when moved in 

 the light : of the belly bluish-white ; the sides have a strong silvery hue. Scales sub-orbi- 

 cular, four lines in diameter, and possessing much pearly lustre. Lateral line straight. 



Form. — Body roundish ; in profile lanceolate. Head long and compressed with a flat- 

 tened vertex. The sagittal line rises between the orbits into a smooth acute ridge. Orbits 

 large, oval, situated as near again to the tip of the snout as to the edge of the gill-cover. The 

 sub-orbitar bones, apparently about six in number, form a circular plate mostly posterior to 

 the eye ; a narrow process runs under the eye to the anterior orbitar, which is sub-orbicular 

 and radiated on the surface. Nostrils close to the orbit : the anterior opening has a raised 

 margin, and is contiguous to the posterior one. The intermaxillaries, forming about one-third 

 of the border of the upper jaw, lie transversely, overlapping the curved articular ends of the 

 labials, and giving a truncated form to the snout. The labials, thick and strong, have a lan- 

 ceolate shape ; they are articulated with the cartilaginous ends of the palate-bones through 

 the medium of a small curved process. The under jaw is strong, and has broad, flat sides 

 with an obtuse and slightly-knobbed extremity, which projects four or five lines beyond the 

 upper jaw : its articulation being as far back as the posterior edge of the orbit, admits of con- 

 siderable depression, but the opening of the mouth is not of corresponding magnitude, for it is 

 contracted by a fold of integument which extends from the middle of the labial to the side of 

 the lower jaw. 



Teeth. — The intermaxillaries, extremity of the lower jaw, vomer, palate-bones, and tongue, 

 are armed with narrow bands of teeth " en velours," 1 as are also the root of the tongue and 

 the superior and inferior pharyngeal bones. 



Gill-covers. — The operculum and suboperculum form a very regular semicircle by the union 

 of their posterior edges. The preoperculum is much curved, and includes a naked cheek, 

 not wider than itself, between it and the sub-orbitars. The gill-openings are large : the mem- 

 branes contain ten flat rays. The branchial rakers are rigid, awl-shaped, and rough interiorly, 

 with minute teeth : those on the upper arch exceed half an inch in length, the others are 

 smaller. 



Fins.— Br. 10; D. 15—0; P. 17, V. 12; A. 18; C. 22$. 



The dorsal, opposed to the ve; Urals, is about its length nearer to the caudal fin than to the 



