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. Argyrosomus, 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 

 bones of the head generally shortened. 

 ^ 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 Coregonus, 2. 



|:j: Supraorbital short, broadly ovate, cap-like ; preorbital com- 

 paratively short and broad; maxillary short and rather 

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

 plementary bone narrow and sharply elliptical ; mouth 



very email, the snout more or less produced. 



Prosopium, 3. 



/. ARGYROSOMUS, Ao-assiz. 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. (AUosomus, Jordan.) 



1. A. iuliibee, (Rich.) Ag. Depth 3 in length; at 

 posterior point of adipose fin equal to length of cau- 

 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, 



16 



