8 



PROCEEDINGS OF THE NATIONAL MUSEUM 



form and for neritic populations from Puget Sound and Alexander 

 Archipelago. The change with age to a flatter pereonite 1 is evident; 

 the figure also demonstrates that in this character the Alexander 

 Archipelago population is intermediate between the oceanic and 

 Puget Sound populations, but is closer, as might be expected, to the 

 other neritic population from Puget Sound. 



14 



JZ 

 t- 

 O 

 Z 

 UJ 



> 



o 



CQ 



10 



A /VV\ A 



A A 



A 



A 



A 



D 



n 



50 40 



■1/ CYPHOS INDEX i 



30 



20 



Figure 6. — Relation between cyphos index and body length in oceanic (triangles), Puget 

 Sound (circles), and Revillagigedo Channel (squares) populations of Cyphocaris challengeri. 



Length of process of pereopod 5 basis. —In figure 7 the ratio 

 of the length of the process of the basis to the length of the distal 

 segments of the limb is plotted against body length. The ratio is 

 clearly higher in the oceanic form and does not appear to vary with 

 age. In figure 8 the ratios obtained for the three populations, lump- 

 ing aU growth stages, are represented according to the graphical 

 method of Hubbs and Hubbs (1953). The wide separation of the 

 oceanic from the two neritic populations is evident. The difference 

 between the means of the latter populations is statistically significant 



