6 U.S. NATIONAL MUSEUM BULLETIN 295 



because of the high probability that Bairdia s. s. belongs here, as 

 well as many other extinct genera. 



Within the subfamily Bairdiinae at least nine genera or subgenera 

 may be distinguished. Three of these taxa already have available 

 names (Triebelina, Bairdoppilata, and Glyptobairdia) . For each of 

 these categories the new soft-part data reinforce the distinctiveness 

 of the taxon that has long been deduced from carapace structure. 

 The remaining species of "Bairdia," by far the majority, fall naturally 

 into two major groups for which the new names Neonesidea and 

 Paranesidea are proposed. These five genera and subgenera are easily 

 recognizable by muscle-scar patterns alone (see Figure 3) ; comparable 

 distinctiveness is suspected but not yet proved for scars of the un- 

 named species-groups within Neonesidea and Paranesidea. 



Neonesidea, to which the majority of described Recent species of 

 "Bairdia" belong, contains three morphologic groups that will deserve 

 at least subgeneric status when better information is available for 

 their diagnosis. The carapace morphology, and perhaps also appendage 

 anatomy, of certain cold- or deepwater species assigned here to 

 Paranesidea and B. (Bairdoppilata) is sufficiently unlike that of the 

 typical shallow-water tropical forms that separate taxa will be re- 

 quired ultimately for them. Finally, at least three species are indicated 

 with morphologic characters intermediate between Neonesidea and 

 Paranesidea. Establishment of these new taxa should be postponed 

 until more species may be investigated. 



The differences in carapace and appendage anatomy between 

 Triebelina and Paranesidea are insufficient to support the family- 

 level distinction of KoUmann (1963). In fact, on the scale established 

 by the other generic diagnoses of this report, they might have been 

 established as subgenera of one genus, which would have then retained 

 the older name Triebelina. However, it seems undesirable to sub- 

 merge the identity of the numerically small and morphologically 

 strictly defined Triebelina by the widespread and heteromorphic 

 form Paranesidea, whose limits and ancestry are at present only 

 conjectural. 



A brief comparison of the essential anatomical features of these 

 five genera and subgenera of Bairdiinae is presented in Table 2. 



Species assigned to Bythocypris in this report include several abyssal 

 species for which a new genus or subgenus should be named, but the 

 absence of described male anatomy for typical European species 

 renders Bythocypris diflBcult to diagnose. The peculiar form 

 Anchistrocheles is herein reinstated by description of new and pre- 

 viously established species. A morphologically intermediate genus, 

 Zabythocypris, is proposed for a distinctive group of rare but character- 

 istic abyssal species. 



