419 



other in color and shape, has been hitherto considered as confined 

 to Europe. But on the 29th of October a fish of the latter spe- 

 cies was caught in the Merrimac River, and examined by him — 

 another example of Arctic species coming down on the American 

 as well as the European coast. 



In the family of Salmonida^, Cuvier unites the abdominal fishes 

 with an adipose fin, and a peculiar structure of the upper jaw — 

 the maxillary and intermaxillary forming a continuous arch. 

 J. Mliller has more recently pointed out structural differences in 

 this family. In those Salmonida3 having no pseudobranchia, he 

 found some with complicated anterior vertebra;, and such he 

 called Characini — others, with the maxillary and intermaxillary 

 bones united side to side into an immovable arch, he called Sco- 

 pelini. The true salmons belong entirely to Arctic and cold 

 regions — the Characini are tropical and fresh-water species of 

 America and Africa, being absent from Asia and Australia — the 

 Scopelini are marine, and of the temperate and warm regions. 

 The dentition of Characini is peculiar, varying much in different 

 members of the family ; in a new genus Analcestis, Ag., from 

 Rio Remak, Peru, resembling Chalceus, Cuv., there are no 

 canines behind the multicuspidate grinders. He had ascertained 

 by direct compai-ison that the species of different basins are dif- 

 ferent, though belonging to the same genus ; many species con- 

 sidered identical by Valenciennes will no doubt prove to be dis- 

 tinct. The Chai'acini are now known to extend beyond South 

 America into Texas and Cuba, and they are probably numerous 

 in Central America. 



In the course of a discussion on the so-called migrations of 

 fishes. Prof. Agassiz referred to the well-known return of the 

 salmon to the rivers where they were born — and said that what 

 has been called migration, as in the case of the shad, is only the 

 successive arrival of diffei'ent individuals, (as the whole number is 

 going northward to spawn,) in different latitudes and in different 

 months, later according to the increase of latitude. Upon this 

 subject very little is known ; but it is certain that fish do not 

 always approach the shore to get into warmer water ; they may 

 perhaps do so to be relieved from the pi-essure of great depths. 



Dr. Brewer observed that the European Widgeon, occasionally 



