176 PROCEEDINGS OF THE NATIONAL MUSEUM vol.108 



RiDGEWAYliDAE, new family 



Copepoda, Calanoida. Detailed diagnostic characters as given 

 above for the unique genus Ridgewayia. Characterized principally 

 by the combination of unreduced and little-specialized cephalic 

 appendages, weakly geniculate right male antennule, fully segmented 

 legs 1-4, and distinctively modified but biramose fifth legs in both 

 sexes. 



Type and only known genus (as herein defined): Ridgewayia 

 Thompson and A. Scott (1903). 



Gurney (1931, p. 84) has outlined a grouping of the calanoid fam- 

 ilies that is taxonomically very useful. For the most part, the new 

 family Ridgewayiidae is taxonomically referable to the definition of 

 the first group, the Centropagina. Gurney considered this group to 

 represent the most primitive of the Calanoida and to be closely allied 

 to another group which included only the Calanidae. Within the 

 Centropagina there are some genera with highly modified fifth legs 

 and reduced endopods (such as Isias), so there would appear little 

 reason to exclude Ridgewayia because of the complexity of the left 

 exopod and modification of the endopods of the male fifth legs. The 

 more primitive segmentation of the antennule found in the new Tor- 

 tugas species emphasizes rather than negates relationship with this 

 group. However, when the phylogenetic position of this family is 

 considered it is probable that important significance must be given 

 to the segmentation of the geniculate antennule in relation to the 

 seemingly unusual position of the hinge. Too little is known to eval- 

 uate this at present, and Ridgewayia appears as a highly singular 

 genus exhibiting a combination of primitive characters with others 

 of unique or specialized modification. For taxonomic purposes, how- 

 ever, the Ridgewayiidae may be currently placed with Gurney's 

 Centropagina or considered allied to that group. 



Similar taxonomic considerations may apply, with some qualifica- 

 tions, to the Pseudocyclopidae, placed by Gurney in an undefined 

 group of "uncertain position." Gurney's concept of the Pseudocyl- 

 opidae may have been somewhat in error inasmuch as he appears to 

 have considered it as including the very anomalous genus Platycopia, 

 which he spoke of as being "related to Psevdocyclops" (1931, p. 82). 

 As has been pointed out (M. S. Wilson, 1946), Platycopia is unique 

 among known calanoids and cannot be closely related to any known 

 genus. Nor is there any known allied family as implied by Lang 

 (1948, pp. 24, 26) in his reference to "Platycopiidae and closely allied 

 families." Lang has placed the Platycopiidae in a suborder separate 

 from the Calanoida. Nomenclaturally, Lang's system has the regret- 

 table and inconvenient effect of eliminating entirely the much-used 



