8(7) Distal segment of pleopod 1 more or less subrectangular (Fig. 



18B) . Cannula of pleopod 2 triangular in shape, not markedly 

 thickened on outer margin (Figs 18D, E, 19A-J) ; shape of end- 

 opod and proportions of segments as in Fig, 18C. (Table 1): 



A. vacovitzai raoovitsai 

 Distal segment of pleopod 1 more or less subovate (Fig. 20A-H) . 

 Cannula of pleopod 2 not conspicuously triangular in shape, 

 and outer margin thickened (Figs 21D, E, 22A-F) ; shape of 

 endopod and proportions of segments as in Fig. 21C. (Table 1) : 



A. vacovitzai australis 



Fig. 19. A. vacovitzai vacovitzai. Variation in morphology of tip of 

 endopod of second pleopod. A-J, ventral views; A-H, J, specimens 

 from eastern States and southeastern Canada; 1, specimen from Washing- 

 ton. From Williams (1970). 



27 



