NO. 3588 PELAGIC AMPHIPOD — BOWMAN AND McCAIN 7 



Channel, Alexander Archipelago, are intermediate, but appear to show 



more resemblance to the Paget Sound than to the oceanic specimens. 



In order to express quantitatively the shape of pereonite 1, a 



sunple index has been devised. The straight-line distance between 



Figure S.— Anterior end of Cyphocaris challengeri, lateral (^^X100=cyphos indexj^ 



the anterodorsal and posterodorsal margins, viewed laterally, is 

 divided into the longest perpendicular from this line to the dorsal 

 margin (fig. 5). The quotient is multiplied by 100 to give an index 

 which may be termed the "cyphos index" (from Ki;0os="hump," 

 the first part of the generic name (7?/pAocam= "hump-head"). In 

 figure 6, cyphos indices are plotted against body length for the oceanic 



