THE COPEPOD GENUS PARANTHESSIUS — ILLG 405 



expanded, arched plate with highly chitinized margins (fig. 34, B). 

 The distal three segments constitute a terminal whip, much narrower, 

 more C3dindrical, and with less departure from the usual lichomolgid 

 structure (fig. 33, B). The first segment has a very mobile articula- 

 tion with the second, which as usual is the longest segment of the 

 antennule. The limit between the second and third segments is trace- 

 able by distinct but incomplete sutures, and a considerable partial fu- 

 sion unites them. The articulation between the third and fourth seg- 

 ments is a complete one. The first segment bears four setae on the 

 anterolateral corner. The second segment bears 13 setae arranged as 

 a fairly dense row along the anterolateral margin. The third seg- 

 ment bears two setae on the distolateral corner. The fourth segment 

 bears three setae on the anterolateral margin, one proximal, the others 

 at the distal corner. The most distal of these is the longest seta of the 

 antennule. The fifth segment, which is the longest of the distal trio, 

 bears three setae. The sixth segment, just slightly shorter than the 

 fifth, bears two setae. The short seventh segment bears four apical 

 setae and four in a subapical position. 



The antenna is 4-segmented. The second segment is much longer 

 than the others and is somewhat flattened dorsoventrally, expanded 

 mediolaterally. The heavy claw borne on the terminal segment is so 

 oriented with the antenna that the dissected appendage takes a position 

 which presents a deceptive narrowness of the second segment (fig. 33, 

 C) . The first and second segments each bear a single seta. The third 

 segment bears four setae. The terminal segment, in addition to its 

 large claw, has three setae, all placed at the base of the claw. 



The mandible is the characteristic flat blade, tapering to a pointed 

 flexible tip, with ciliate margins (as seen in the illustrated mandible 

 of Paranthessius tivelae, fig. 36, I). The maxillule bears two termi- 

 nally placed setae. Figure 34, K, presents the mouth parts of an imma- 

 ture individual in which there is complete correspondence to the adult 

 female. 



The maxilla is 2-segiTiented. The base is very large ; its posterior 

 margin bears a row of spinules. The terminal joint bears an unorna- 

 mented proximal seta and a more distal, larger seta with cilia arranged 

 along its posteromedial margin. 



The maxilliped is very reduced, consisting of three simple segments, 

 the terminal segment the shortest (fig. 33, D). 



The swimming legs conform to the characteristic pattern for the 

 genus. The arrangement of spines and setae on the segments of the 

 rami follows : 



First leg, exopoclite: First segment (basal) bears a lateral spine; 

 second segment bears a lateral spine and a medial seta ; third segment 

 (terminal) bears four spines and four setae. Endopodite: First seg- 



