172 PROCEEDINGS OF THE NATIONAL MUSEUM vol. los 



first and second segments are present and strongly developed, being 

 nearly as long as the exopod itself. These spines are placed close to- 

 gether, the second segment being much reduced on the outer side. 

 The apical portion appears to be structurally comparable to the modi- 

 fied third segment of the American species. Its simplicity may be 

 due to reduction or lack of some of the processes and fragmented 

 membranes that complicate the structure in the other species, but it 

 is certainly to be correlated with them. Indeed, it appears much like 

 this portion of the exopod in the Tortugas specimens whenever they 

 were viewed under relatively low power (fig. 35). Examination at 

 high magnification with oil immersion objectives might well reveal 

 complex detail in the Madras species such as has been found to exist 

 in the American species. &ishnaswamy's (1953) unnamed specimen 

 is therefore seemingly relatable to these species through the fifth leg. 

 In the presence of setae on the right endopod, in the lack of the second 

 outer spine of the right exopod 2, and in the seeming reduction of the 

 left exopod it represents a possible link between the American species 

 and canalis. In the case of this latter species, however, the structure 

 of the apical portion of the left exopod may be somewhat different. 

 As drawn by Gurney (1927) it has a flattened appearance and is dif- 

 ficult to reconcile exactly with the observed species. Such a differ- 

 ence may be entirely graphic in nature. Here again there is need for 

 further examination, and probably also comparison with actual 

 specimens of some of the other species. 



Both of the Tortugas species have the first basipod segments fused 

 and comparatively reduced. Unfortunately, Esterly (1911) has not 

 shown or described the basipods completely for marki. In his illustra- 

 tions the legs are entirely separated. A reduced but separated seg- 

 ment is shown for the right leg, but only a portion of the left second 

 basipod segment is included. It would be instructive to know the 

 exact condition, since marki and the Tortugas species are obviously 

 congeneric. Gurney shows well-developed segments joined by a 

 center connecting plate very similar to that of the subadult Tortugas 

 male (fig. 36). Apparently the first basipod segments are well de- 

 veloped and separated in the Madras specimen. Correlated with 

 other differences, the lack of fusion may have generic or other taxo- 

 nomic significance, and it is a character that should be carefully noted. 



It is difiicult to interpret the fifth leg of the subadult male (Ridge- 

 ivayia sp., Tortugas) in relation to the appendage in the adult. If it 

 does represent a copepodid stage of one of the two known Tortugas 

 species, then considerable change must take place between stage V 

 and the molt to the adult. This would involve fusion of the basal 

 segments, loss of one spine of the apex of the right exopod, and loss of 

 the inner setae of the exopod and of the endopod. However, since 



