THE COPEPOD GENUS PARANTHESSIUS — ILLG 407 



The state of preservation of my specimens is not favorable for deter- 

 mining details of internal anatomy, so the exact identity of the ovif er- 

 ous bands has not been established. The typical position of the 

 ovaries and oviducts in lichomolgids is in the thoracic segments, with 

 no extension posterior to the apertures of the oviducts on the genital 

 segment. 



The caudal rami are about four times as long as wide (fig. 34, E). 

 The proximal lateral seta is placed relatively far posteriorly, at about 

 two-fifths the length of the ramus. The external seta is longer than 

 the internal. The two longest central setae of the tip of the ramus 

 are jointed at their bases; the longer is about two and one-half times 

 the length of the caudal ramus. 



Length of the body, exclusive of the setae of the caudal rami, is 2 

 mm. 



Male: The body habit retains the tendency to elongation of the 

 female, but not in such extreme form ; there is therefore little depar- 

 ture from the facies of the typical lichomolgid male. The segmenta- 

 tion of the metasome is the same in the two sexes. In the urosome, 

 the genital thoracic segment of the male is a free somite and bears 

 well-developed sixth legs. The separation of the first abdominal 

 somite from the genital segment results in a urosome of six segments. 

 The more extreme development of the rostrum of the male in com- 

 parison to the condition in the female has been described above (fig. 

 34, F) . The antennule is alike in the two sexes. 



The antenna bears out a tendency in the dimorphism of the species 

 of Paranthessius I have seen toward an increase in number and size 

 of spinous protuberances of the appendages. The second segment 

 of the male antennule bears a row of spinules which are much stouter 

 and longer than those seen in the female. The mandibles, maxillules, 

 and maxillae do not exhibit dimorphism. 



The maxilliped is one of the diagnostic structures of the male (fig. 34, 

 G) . The appendage is the largest and most conspicuous of the mouth 

 parts. Of the three segments, the basal one is the shortest. The 

 second segment is stout and long, its length about double the width. 

 The terminal segment is parallel with and appressed to the second 

 segment and, by a complicated articulation, forms a subchelate ap- 

 pendage with that segment. The terminal segment is a long narrow 

 blade, about one and one-half times the length of the second segment. 

 A seta, of curiously modified character, is borne on the second segment. 

 A long seta is borne on the basal portion of the terminal segment. 

 Stout spinules, set in rows, ornament the medial surface of the second 

 joint. 



In the swimming legs the sex of adults might be determined by the 

 more spinous ornamentation of the limbs of the males. The fringes 



818707—49 ?, 



