158 PROCEEDINGS OF THE NATIONAL MUSEUM vol. lis 



fourths of segment covered by single, platelike structure distinctly 

 separate from genital segment. Division between fourth thoracic leg- 

 bearing segment and genital segment distinct (fig. 66). 



Genital segment longer than wide, median and posterior lateral 

 margins parallel. Posterior lateral sm-faces extending past junction of 

 abdomen and genital segment; posterior margin forming sharp angle 

 with lateral margin, middle of posterior margin slightly concave. 

 Genital segment with two pairs of lobate processes projecting from 

 posterior ventral surface (fig. 6/). 



General outline of abdomen obovoid; length about three-fourths 

 length of genital segment, greatest width more than half length. 



Cephalothorax of C. constrictus circular, not ovoid as in C. randalli. 

 Fourth thoracic leg-bearing segment of C. constrictus longer than that 

 of C. randalli, anterior portion similar to C. randalli, posterior portion 

 forming short, necklike extension; without platelike structure present 

 in C. randalli (fig. 6c). Posterior lateral surfaces of genital segment 

 forming lobate instead of angular projections (fig. 6(/). Length of abdo- 

 men about one-third length of genital segment in contrast to relatively 

 longer length of abdomen of C. randalli; greatest width four-fifths 

 greatest length. 



Antennule of C. randalli two-segmented, excluding frontal plate, 

 attached to ventral surface of frontal region and cephalothorax just 

 lateral to base of lunule ; outer, free margin of lunule overlapping base 

 of first segment of antennule. First segment of antennule broad, 

 greatest width two-thirds greatest length. Anterior surface with 

 approximately twenty plumose setae. Second segment elongate, 

 greatest length 1.3 times that of first segment. Second segment 

 with naked seta from distal portion of posterior margin, eleven 

 naked setae from distal surface (fig. 6A). 



Second antenna of C. randalli three-segmented, attached just 

 posterior and medial to antennule. First segment forming broad, 

 flat articular surface, with small, laterally directed, lappet-like pro- 

 trusion. Second segment short, slightly longer than wide; proximal 

 end slightly wider than distal. Second segment bearing small, lobate 

 projection from inner distal surface. Third segment, including ter- 

 minal process, elongate, length greater than two times that of second 

 segment. Terminal process of third segment broadly curved, division 

 between segment and process indistinct; inner terminal surface of 

 process with minute, toothlike projections (fig. 6i). 



Second antenna of C. constrictus similar to that of C. randalli though 

 possessing two seta-like processes on terminal process of third segment; 

 processes absent on C. randalli. 



Mandible of C. randalli four-parted. First part sHghtly broader 

 proximally than distally. Second part short, approximately two- 



