406 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 99 



ment — medial seta ; second segment — medial seta ; third segment — one 

 spine and four setae. 



Second leg, exopodite: First segment — lateral spine; second seg- 

 ment — lateral spine and medial seta ; third segment — four spines and 

 five setae. Endopodite : first segment — medial seta ; second segment — 

 two medial setae ; third segment — three spines and three setae. 



Third leg, exopodite: First segment — lateral spine; second seg- 

 ment — lateral spine, medial seta ; third segment — four spines and five 

 setae, Endopodite: first segment — medial seta; second segment — two 

 medial setae ; third segment — three spines and two setae. 



Fourth leg, exopodite: First segment — lateral spine; second seg- 

 ment — lateral spine, medial seta; third segment — three spines and 

 five setae. Endopodite : first segment — medial seta ; second segment — 

 medial seta; third segment — two terminal spines, the lateral about 

 three-fifths of the length of the medial (fig. 33, E). 



In all the pairs of swimming legs, the distal margins of the basipo- 

 dites are set with very close-set, long, fine spinules which form a con- 

 spicuous fringe. The basis in each leg bears a small lateral seta just 

 proximal to the articulation of the exopodite with the basis. The 

 coxa bears a large ciliated seta at its medial distal corner. The mar- 

 gins of the rami are ciliated to varying degrees. 



The fifth leg possesses a very elongate free segment (length three 

 or more times the width), which is directed somewhat posteriorly. 

 A dorsal seta, set on the body somite proper, represents the basis of 

 the fifth leg. The terminal armature of the free segment comprises 

 a shorter, lateral setif orm member and a slightly longer, much stouter, 

 medial spine (fig. 33, F) . 



The urosome is elongate, exceeding slightly the metasome. The 

 urosome comprises the sixth thoracic segment (which bears the fifth 

 legs) ; the genital segment, a fused composite of the seventh thoracic 

 segment and the first abdominal somite; and three free abdominal 

 segments. In all these, the posterior margins are entire, lacking the 

 spinous serrations characteristics of some other species. The termi- 

 nal segment exhibits an unique form of ornamentation. About mid- 

 way in length of the segment is placed across the ventral surface a 

 pair of rows of slender, elongate spinules, in fringe arrangement. 

 The rows do not meet at the midline, and they form arches across 

 the ventral surface nearly to its lateral extent. The number of spin- 

 ules per row in specimens examined has varied from approximately 

 15 to 20 in each row (fig. 34, C) . 



Perhaps a significant anticipation of the encroachment of the whole 

 body by reproductive structures in the most degenerate parasitic 

 copepods is provided in this species where the ovarian (or oviducal) 

 tubes of the two sides of the body extend into the abdomen, on one 

 side, at least, usually penetrating the terminal segment (fig. 34, D). 



