Proceedings of 

 the United States 

 National Museum 



SMITHSONIAN INSTITUTION • WASHINGTON, D.C. 



Volume 122 1967 Number 3588 



VARIATION AND DISTRIBUTION OF THE 



PELAGIC AMPHIPOD CYPHOCARIS CHALLENGERI 



IN THE NORTHEAST PACIFIC 



(GAMMARIDEA: LYSIANASSIDAE) 



By Thomas E. Bowman and John C. McCain 



Associate and Assistant Curators, Division of Crustacea 



The most common epipelagic gammaridean amphipod in Subarctic 

 Water of the North Pacific is Cyphocaris challengeri Stebbing (f888, 

 pp. 661-664, pi. 17). Other species of Cyphocaris occur in the North 

 Pacific but are usually found at deeper levels than C. challengeri. 



Altho the original description by Stebbing was detailed and well 

 illustrated, it was based on a single juvenile specimen only about 5 mm 

 long. The species was subsequently reported from the North and 

 South Atlantic, the South Pacific, and the Indian Ocean but was 

 not again recorded from the North Pacific until Thorsteinson (1941) 

 reported its presence at Nanaimo, British Columbia. Its occurrence 

 in the western North Pacific has been discussed recently by Birstein 

 and Vinogradov (1955, 1958), who provided a map showing its 

 worldwide distribution (1955, fig. 33). 



In addition to recording the presence of C. challengeri at Nanaimo 

 and giving some data on its variation with age, Thorsteinson described 

 C. kincaidi from the Gulf of Alaska. Thorsteinson's new species was 

 said to differ from C. challengeri in the more sharply produced pereonite 

 1, the more numerous setae on the gnathopods, the longer and narrower 

 process of the basis of pereopod 5, and the longer telson. 



It has been shown that certain characters of C. challengeri change 

 with age: (1) In all species of Cyphocaris the head is directed down- 



1 



