162 PROCEEDINGS OF THE NATIONAL MUSEUM vol. loa 



ever, there are often strildng changes in this appendage between the 

 recognized stage V and the adult, such as is laiown for Centropages 

 (Gurney, 1931). It is therefore impossible to say with absolute 

 certainty that this does not represent the subadult stage of one or the 

 other of the two species. The left antennule in the adult could be 

 25- or 26-segmented, depending upon whether the partially divided 

 ninth segment becomes fused or separated. There is no indication of 

 modification of the right antennule, either in the middle or distal 

 portions. 



One interesting point brought out by examination of this copepodid 

 is that the modified processes of the first leg are not fully developed 

 until the adult stage, although the leg is otherwise like that of the 

 adult. 



Discussion 



The name Ridgewayia was proposed in honor of Sir West Ridgeway, 

 governor of Ceylon. Attention is drawn to this in order to emphasize 

 that the spelling of the generic name is correct. A genus of birds, 

 Ridgwayia Stejneger 1883, named for the ornithologist Robert Ridg- 

 way differs in the spelling by one letter. 



For piu-poses of brevity in the following discussion, the new Tortugas 

 species (gracilis, shoemakeri) and the Bermuda species (marki) are 

 referred to collectively as the American species. 



Specific Differentiation 



Habitus: In general appearance, the species are alike. Only for 

 marki is there a recorded lack of separation of the cephalic and first 

 thoracic somites. Since the separation of this segment in the Tortugas 

 material was not always as distinct as that of the other segments, 

 specimens in future collections of marki should be carefully examined 

 for indistinct or partial separation. There is also need to determine 

 the possible presence of the reduced last urosomal segments in both 

 marki and canalis. Esterly's (1911) drawing of the female shows the 

 caudal rami united basally and suggests the presence of this reduced 

 segment. The urosome of canalis (male) as illustrated is very like 

 that of the subadult male listed herein as Ridgewayia sp. (Tortugas), 

 Gurney (1927) says "Abdomen of four somites" but adds "the 5th 

 somite scarcely distinct," The possibility that Gurney 's specimens 

 were in the subadult stage is dismissed on the basis of the apparent 

 complete development of the first leg, and of Gurnej^'s wide experience 

 in study of developmental stages of copepods, precluding the possi- 

 bility that he would err in this regard, even mth an unfamiliar genus. 



