2 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 122 



ward and partly covered above by the long pereonite 1, which is 

 produced anteriorly into a process. The process varies in shape from 

 low and bluntly rounded to long and sharply pointed. The process 

 is most acute in young specimens and becomes more rounded as a 

 Cyphocaris ages (Schellenberg, 1926b). (2) The number of teeth on 

 the posterior margin of the basis of pereopod 5 decreases with age 

 (Chevreux, 1916; Schellenberg, 1926a; Thorsteinson, 1941). (3) 

 The length of the process of the basis of pereopod 5 increases in pro- 

 portion to the rest of the limb (Thorsteinson, 1941). (4) The length 

 of the telson increases relative to the length of uropod 3 (Schellenberg, 

 1926b). 



In consideration of the variation with age detailed above, Shoe- 

 maker (1945) reduced C. kincaidi to a junior synonym of C. challengeri, 

 an action accepted by subsequent authors (Birstein and Vinogradov, 

 1955, 1958, 1960; Gm-janova, 1962). In recent years, however, we 

 have examined numerous samples collected with plankton nets and 

 Isaacs-Kidd midwater trawls off the west coast of North America, 

 containing larger numbers of Cyphocaris than had been available 

 previously. The fact that almost all of the specimens could be as- 

 signed without difficulty to either C. challengeri or C. kincaidi as 

 defined by Thorsteinson indicated the desirability of a reassessment 

 of Shoemaker's decision to lump them, especially since in our collec- 

 tions the two forms were separated geographically as well as 

 morphologically. 



We wish to thank William Aron, then of the Department of Ocean- 

 ography, University of Washington, for sending us representative 

 samples of amphipods from M/Y Brown Bear Cruises 199 and 202, and 

 Bruce L. Wing, U.S. Bureau of Commercial Fisheries Biological 

 Laboratory, Auke Bay, Alaska, for midwater trawl collections from 

 Lynn Canal, in the Alexander Archipelago, Southeast Alaska. 



Distribution in the North Pacific 



Since the form of the body of C. challengeri (sensu latu, including 

 both C. challengeri and C. kincaidi sensu Thorsteinson) is correlated 

 with its neritic-oceanic distribution, the neritic and oceanic distri- 

 butions will be considered separately. 



Oceanic distribution. — Figure 1 shows the offshore distribution 

 of C. challengeri, based largely on Cruises 1, 5, and 9 of the California 

 Cooperative Oceanic Fisheries Investigations (CalCOFI) in 1949 and 

 Cruises 199 and 202 of the University of Washington M/V Brown Bear 

 in 1958. A few records from collections by the U.S. Bureau of 

 Fisheries Steamer Albatross have been included. 



Altho the CalCOFI cruises extended south about to the latitude of 

 Punta Eugenia, Baja California, almost all the stations positive for 



