COPEPOD GENUS RIDGEWAYIA — WILSON 



173 



two species are known in which the setae are present on the right 

 endopod, it might be predicted that an unknown species with this 

 character is present in Tortugas waters. The apical membranous 

 spines and hyaline processes of the left exopod may or may not be the 

 beginnings of development of the complex armature of the third seg- 

 ment of the adult. Again, they may represent armature belonging 

 to a species that has a simpler development of this part of the exopod, 

 such as shown for canalis. 



The significant characters of the fifth leg have been summarized in 

 table 4. The segmentation and spinal armature of the left exopod of 

 canalis is listed as uncertain (see diagnosis of canalis, p. 145). 



Table 4. — Comparative characters of male leg 5, Ridgewayia 

 (KEY: (+) cbaracter present; (— ) character absent; (?) unknown) 



Key to known species of Ridgewayia 



The following key has been devised to include both sexes and to 

 summarize and emphasize, in part, similarity of known basic charac- 

 ters that may point up generic or species-group distinctions. Un- 

 fortunately, the Madras male cannot be included in the key because 

 of insufficient information. It differs strikingly from all other known 

 males in that the right endopod of the fifth leg reaches beyond the 

 apex of the relatively shortened right exopod. Characters of the 

 caudal setae and antennules used in couplets 3 and 4 need verification 

 in marki. 



1. Antenna, exopod 7-segmented; maxilla with total of 5 lobes, of which one 



belongs to basal segment. (Female unknown.) R. canalis 



Antenna, exopod 8-segmented; maxilla with total of 6-7 lobes, of which more 

 than one belongs to basal segment 2 



2. Maxilla, basal segment with 3 lobes; leg 5 female, exopod 3, innermost spine 



not longer than other spines. (Male unknown.) R. typica 



Maxilla, basal segment with 2 lobes; leg 5 female, exopod 3, innermost spine 

 longer than other spines, about equal to length of segment 3 



