28 U.S. NATIONAL MUSEUM BULLETIN 29 5 



Type specimens. — Adult male holotype USNM 121263; allotype 

 female USNM 121264; paratypes USNM 121265, 121266. 



Type locality. — Anton Bruun cruise 8 station 403F. 



Diagnosis. — Carapace highly rounded and only minimally caudate; 

 posterior margin of right valve fringed, of left valve denticulate, 

 enlarged terminal spine, anterior margins smooth; central and postero- 

 medial ovate opaque areas. 



Antennal claw with anterior portion of hook tapered and much 

 the longer; thoracic legs and claws excessively long and thin; furca 

 with only six setae, setae 1 and 4 of equal length and longer than 

 seta 3, seta 5 shorter, seta 6 shorter still, seta 2 unfeathered; distal 

 lobe of male copulatory organ curved subtriangular in outline, pene- 

 trated near its tip by pointed end of lamellar support for copulatory 

 tube. 



Material. — Three living specimens and 23 subfossil specimens 

 from Anton Bruun stations 371 G and 403F. 



Dimensions.— Adult male USNM 121263, left valve, length 0.95 

 mm, height 0.59 mm; right valve, length 0.95 mm, height 0.57 mm. 



Adult female USNM 121264, left valve, length 0.94 mm, height 

 0.62 mm; right valve, length 0.90 mm, height 0.57 mm. 



Distribution. — Mozambique Channel near Mozambique. 



Neonesidea arenigena, new species 



Figure 9 



Etymology. — Latin arena, sand + -genus, living in. 



Type specimens. — Adult male holotype USNM 121267; allotype 

 female USNM 121268; paratypes USNM 121269-121270. 



Type locality.— Nosy Be, Madagascar, sample 166 (13°38'5" S, 

 47°51' E, depth 23 m; dredge sample near Nosy Iranja). 



Diagnosis. — All carapace margins smooth, exterior completely 

 smooth, rounded subdeltoid in lateral view, muscle scars compactly 

 grouped into 4 wedge-shaped clusters. 



Both points of antennal claw bluntly rounded, anterior one slightly 

 longer; furca with 7 setae, setae 5, 6, and 7 extremely short; copula- 

 tory organ foreshortened, terminal lobe blunt, not penetrated by 

 copulatory tube. 



Material. — Nosy Be; 5 living specimens, 387 subfossil specimens. 



Dimensions.— Adult male USNM 121267, left valve, length 0.80 

 mm, height 0.53 mm; right valve, length 0.79 mm, height 0.44 mm. 



Adult female USNM 121268, left valve, length 0.74 mm, height 

 0.48 mm; right valve, length 0.74 mm, height 0.36. 



Habitat. — This is the only bairdian species consistently collected 

 living in sandy sediments around Nosy Be (twice in shallow-water 

 dredgings, once in sand-impregnated loose alga at low tide level). 



