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PROCEEDINGS OF THE NATIONAL MUSEUM 



(fig. 34, A) . A most curious feature of the sexual dimorphism of this 

 species is the fact that in the males the auxiliary knobs are still more 

 strongly produced as stout spines, directed ventrally and posteriorly, 

 each equal to nearly half the length of the principal beak (fig. 34, F). 

 The antennule is unique among members of the genus so far de- 

 scribed. The proximal four segments are intricately related in an 



Figure 3-i.—Paranthessius columhiae (Thompson): Female, A, rostral spine (X 144); B, 

 basal segments of antennule (X 296); C, last abdominal segment (X 144); D, abdomen 

 (X 42); E, caudal ramus (X 144). Male, F, rostrum and bases of antennules (X 144); 

 G, maxilliped (X 144); H, fifth leg (X 424). Fifth copepodid, male, I, maxilliped of 

 young example (X 296); J, maxilliped of individual about to molt (X 296). Fourth 

 COPEPODID, K, mouth parts (X 296; LA, upper lip; MN, base of mandible; M, maxillule; 

 MX, maxilla; MP, maxilliped); L, sixth and seventh thoracic somites (X 144). 



