A (T)MPARLSOX OF THE CHUB-MACKERELS OF THE 

 ATLANTIC AND PACIFIC OCEANS. 



By Barton Warren Evermann 



and 



William Converse Kendall, 



Of the U. S. /inn a a of Fisheries. 



For a number of years the chub-mackerels, otherwise more or less 

 locally known as Thimble-eye, Bulls-eye, and Hard-head mackerel, 

 of both the Atlantic and Pacific oceans have been considered as one 

 species of almost cosmopolitan distribution, bearing the name 

 Scomber colias Gmelin (1788). More recently Doctor Jordan has 

 assigned to them the earlier name, Scomber japonicus, under which 

 the Japanese fish was described by Huttuyn (1782). 



Recently we have had an opportunity to compare two specimens 

 of chub-mackerel from Peru with several from Rhode Island, and find 

 certain conspicuous differences. Further evidence was obtained by 

 comparison of a number of specimens from several localities in both 

 the Atlantic and Pacific, which showed the same differences as well 

 as others of slighter importance. The most pronounced difference 

 is in the size of the head which is proportionately longer in the 

 Pacific form. The minor differences are in the positions of the 

 dorsal and ventral fins. In the Atlantic form the first or spinous 

 dorsal is inserted nearer the tip of the snout, and there is a greater 

 distance between its origin and the origin of the second dorsal than 

 in the Pacific fish. In the Atlantic fish, too, Hie distance between 

 the tip of the lower jaw and the base of the ventral is shorter than 

 in the Pacific specimens. 



These differences are shown in the tables that follow. 



Proceedings U.S. National Museum, Vol. 38 No. 1748. 



