ARGYEOSOMUS — CISCOES 53 



curved backwards and slightly inwards, and the posterior pair 

 much smaller and directed almost exactly inwards. These 

 teeth disappear as the fish grows up, the food changing likewise 

 until, in the adult, it consists mainly of small mollusks and 

 crustaceans, with larvae of insects and other animal forms. 

 The gill-rakers of the adult are of a size and number to enable 

 it to separate from the water organisms as small as Entomostraca, 

 and where these are abundant they make a large percentage 

 of the food. The general character of the contents of the 

 stomach indicates, however, that the fish feeds habitually at 

 the bottom, as might indeed be inferred from the character of its 

 mouth. In aquaria it has been forced to feed on small fish in 

 winter, and has learned to pursue and seize its prey much as a 

 trout would do. 



It is caught mainly in gill- and pound-nets from April to 

 the end of December. It is not properly an angler's fish, 

 although where abundant it may be taken on the hook with a 

 bait of worms or insect larvae. Fortunately for the future of 

 the species, this valuable and popular food-fish is one of those 

 best adapted to artificial propagation. Females are adult in 

 three or four years, and 75 to 95 per cent, of their eggs yield 

 the young in the hatchery. 



A single other species of the genus Coregonus (C. quadri- 

 lateraUs, the round or Menominee whitefish) is taken in Lake 

 Michigan, though much more rarely than the common w^hite- 

 fish. A 'Sufficient characterization of this species will be found 

 in the key to the species of Coregonus preceding. 



Genus ARGYROSOMUS Agassiz 



CISCOES 



Close to Coregonus, from which it differs chiefly in the larger mouth 

 and more produced jaws, the premaxillaries being placed nearly horizontally, 

 and the lower jaw projecting decidedly beyond them; gill-rakers very long 

 and slender; dorsal fin of 9 to 12 rays; caudal forked; scales, etc., as in Core- 

 gonus] vertebrae 55. Fresh waters of northern Europe, Asia, and North 

 America. Species numerous; about 6 known from the Great Lake region 

 of the United States. 



