REVISION OF RECENT BAIRDIIDAE 41 



Antenna quite robust, fifth podomere no more than twice as long 

 as fourth; distal claw smooth and simply tapering in both sexes; 

 anterodistal seta short and thin in male, long but thin in female; fused 

 claw of sixth podomere conspicuously serrate or even pectinate in 

 male, finely but visibly serrate in female. Vibratory plate of first 

 thoracic leg with the four unfeathered setae segregated proximally, of 

 equal or diminishing lengths; thoracic legs with podomere 4 no more 

 than twice as long as podomere 5. Furca with 6 setae, setae 5 and 6 

 extremely tiny. Copulatory organ variable in form but generally very 

 massive, with great hemicircular median lobe, smaller oblong or 

 globose distal lobe, the junction between these lobes usually obscure; 

 having one or more very strongly chitinized conical or digitiform 

 projections, other less sharply defined swellings, and/or setae; copu- 

 latory tube rather short but stout, may be curved in sigmoid fashion 

 or nearly straight, without long flexible continuation. 



Species included. — Recent species whose soft parts have been 

 described, listed by original binomen: 



Bairdia arostrata Kornicker, 1961 

 Bairdia gigacantha Kornicker, 1961 

 Bairdia harpago Kornicker, 1961 

 Paranesidea algicola, new species 

 Paranesidea cheroconcha, new species 

 Paranesidea fradicorallicola, new species 

 Paranesidea spongicola, new species 



Ecology.— This, the second most abundant group of "Bairdia" 

 species, is abundantly represented in tropical faunas. These species 

 are characteristic of very shallow water, chiefly inhabiting the surfaces 

 of algae, sponges, corals, coralline detritus, and associated marine 

 organisms on coral reefs and in nearby inner sublittoral environments. 

 They are apparently absent from intertidal and other variably saline 

 conditions. The two abyssal species assigned below to Paranesidea do 

 not conform to this genus in either morphology or ecology and would 

 better be relegated to a new genus. 



Distribution. — Of bairdian species whose soft parts are known, 

 only those described by Kornicker (1961) from the Bahamas can 

 definitely be assigned to Paranesidea. 



Affinities. — The carapace and appendage anatomy of this group 

 is essentially continuous with that of Triebelina, and it is, in fact, 

 difficult to know how or where to define a boundary between the two 

 genera on appendage criteria alone. In part this difficulty arises from 

 the lack of described male specimens of Triebelina. The rough texture 

 and subquadrate carapace outline of Triebelina represent extreme 

 development of the tendency toward robust punctate carapace in 

 Paranesidea. 



