PARASITIC COPEPOD CRUSTACEANS — LEWIS 



137 



cephalothoracic grooves forming irregular H, cross groove in pos- 

 terior thii'd of cephalo thorax; anterior longitudinal grooves extending 

 anteriorly, in ii-regular manner, to ocular region, turning laterally 

 abruptly and terminating at indentation of anterior lateral cephalo- 

 thoracic margin. Eyes distinct, with two small orbicular crystalline 

 body at outer edge of regions of dark pigmentation, pigmented regions 

 contiguous on median longitudinal axis of body. 



I.Omm. 



Figure 36.—Alebion gracilis V^Wson, 1905, female: a, dorsal view; b, posterior cephalotho- 

 racic region and fourth pedigerous segment, dorsal view; c, fourth pedigerous segment, 

 genital segment, abdomen, and caudal ramus, ventral view. 



Free fourth pedigerous segment (figs. 366, c) narrow, slightly less 

 than one-fourth the width of cephalothorax, distinct from cephalo- 

 thorax and genital segment, attached to short, necklike extension of 

 median cephalothoracic region. Segment with pair of alae pro- 

 jecting posteriorly from dorsal surface, covering anterior end of 

 genital segment. Wilson (1932) indicates that the distal ends of the 

 alae are squarely truncated. The inner margins of the alae are 

 basically flat, giving the form figured by Wilson (1907a, 1932) but 

 the distal ends are sharply rounded, not truncated. 



Genital segment (fig. 38c) of general heart-shape with posterior end 

 forming sinus. Anterior lateral margins with row of spinules. Pair 



782-215—66 6 



