ADDENDA. 361 



be regarded as genera, although they are much more 

 closely related than the genera of Salmons. These 

 genera or subgenera may be briefly defined as follows: 



* Premaxillaries narrow, placed more or less nearly horizontally, 



the mandible elongate, its tip about even with that of the 

 upper jaw ; the general outline of the muzzle therefore rather 

 pointed; bones of head generally elongate. Aegtkosomds, 1. 

 ** Premaxillaries broad, placed vertically or turned inward, over- 

 lapping the tip of the lower jaw, the general outline of the 

 muzzle therefore rather bluntish or truncate; mandible and 

 hones of the head generally shortened, 

 t Supraorbital elongate ; preorbital long and narrow; maxil- 

 lary comparatively long, reaching to pupil ; the small sup. 

 plemental bone ovate in form, rather broad; mouth not 



very small Cobbgonus, 2. 



tt Supraorbital short, broadly ovate, cap-like ; preorbital com- 

 paratively short and broad ; maxillary short and rather 

 broad, not reaching to the line of the eye ; the small sup- 

 plementary bone narrow and sharply elliptical ; mouth 

 very email, the snout more or less produced. 



Prosopitm, 3. 



/. ARGYROSOMUS, Agassiz. Ciscoes. 



* Body short, deep, compressed, shad-like; the sides strongly 



compressed; curve of the back similar to that of the belly; 

 scales large, notably larger forwards, rather closely imbri- 

 cated, the posterior margin little convex. (Allosormm, Jordan.) 



1. A. iullibee, (Kich.) Ag. Depth 3 in length; at 

 posterior point of adipose fin equal to length of can- 

 dal peduncle, 8^ in length; head 4 in length, conic and 

 compressed; eye 4^ in head; maxillary reaching nearly 

 to middle of eye; jaws equal; tongue with a patch of 

 teeth; D. 2, 11; A. 2, 11; lat. 1. 74, 8 rows above it and 

 7 below; white, each scale with a bright silvery patch, 

 these forming very distinct silvery stripes along the rows 

 of scales. Upper Great Lakes and N. A species of 

 this type occurs also in the eastern part of Lake Erie. 

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