220 NEW YORK STATE MUSEUM 



of the species the lower jaw is included within the upper, the* 

 mouth is small, and the intermaxillary bone broad and more or 

 less vertical in position. These two may be readily distin- 

 guished by the structure of the gill rakers, and the size of the 

 mouth. The remaining five whitefishes have the lower jaw as- 

 long as, or longer than, the upper, the mouth large, and the 

 intermaxillary narrow and not vertical in position. They are 

 easily separated from one another by the shape of the body, 

 and the size and contour of the scales. The relations of the 

 groups are shown in the following key. 



1 Lower jaw shorter than upper. 



1 a Mouth very small, upper jaw not reaching to eye; gill rakers 

 short and stout, 13 to 16 below angle of first arch (P r o s o - 

 pi u m) 



QUA DEI LATE BALIS 



1 & Mouth moderate, upper jaw reaching beyond front of eye; gill 



rakers long and slender, 20 or more below angle of first arch 

 (Coregonus) 



CLUPEIFORMIS 



2 Lower jaw equal to or longer than upper. 



2 a Body slender, elongate; scales small, and convex on their free- 



margin; lower jaw longer than upper (Ar gyros o m u s) 



OSMERIFORMIS ARTEDI, HOYI 



PROGNATHUS 



2 & Body deep, short; scales large, deep, the free margin scarcely 

 convex; jaws equal (Allosomus) 



T U L L I B-E E 



Genus COREGONUS (Artedi) Linnaeus 



Body oblong or elongate, compressed; head more or less coni- 

 cal, compressed, the snout more or less projecting beyond the 

 lower jaw; mouth small, the maxillary short, not extending 

 beyond the orbit, with a well developed supplemental bone; 

 teeth extremely minute, if present; scales moderate, thin, 

 cycloid, rather firm. Dorsal fin moderate; caudal fin deeply 

 forked; anal fin somewhat elongate; ventrals well developed. 

 Pseudobranchiae large; gill rakers varying from short and 

 thickish to long and slender; air bladder very large; vertebrae 

 56 to 60; stomach horseshoe-shaped, with many (about 100) 

 pyloric caeca; ova small. Species about 15, inhabiting the clear- 

 lakes of northern Europe, Asia, and America, in arctic regions 

 , descending to the sea. Most of them spawn in late fall or 



