22 U.S. NATIONAL MUSEUM BULLETIN 295 



longer curved terminal spine. Hinge elements very finely crenulate, 

 thin. 



Copulatory organ of male with slender median and terminal lobes; 

 slender lamelHform support of copulatory tube of equal thickness 

 throughout, tube penetrating distal end of terminal lobe near tiny 

 crescentic projection, continuing as short thread. 



Material. — Nosy Be; 445 living specimens, 293 subfossil speci- 

 mens. 



Single living specimens collected at Anse Royale, Ghardaqua, and 

 Anton Bruun 412L. USNM 121252-121257. 



Dimensions. — Adult male USNM 121252, left valve, length in- 

 cluding spine 1.09 mm, length without spine 1.02 mm, height 0.57 

 mm; right valve, length 1.03 mm, height 0.52 mm. 



Adult female USNM 121253, left valve, length including spine, 1.06 

 mm, length without spine 1.01 mm, height 0.61 mm; right valve, 

 length 1.01 mm, height 0.57 mm. 



Habitat. — Nosy Be; the most abundant bairdian species in the 

 epifauna of algae, grasses, sponges, corals, and dead coral fragments in 

 coral reef and submerged platform habitats. 



Subfossil distribution. — Nosy Be; moderately common in 

 shallow-water sands, especially near reefs. 



Affinities. — The Nosy Be specimens are identical with the 

 Ghardaqua specimen. 



Hartmann (1964), noting the minute striations on the hinge elements 

 of this form, similar to those illustrated for Bairdia coronata Brady 

 (then assigned to Triebelina) by van Morkhoven (1958, pi. 46: fig. 4), 

 placed this species in Triebelina, as he had done earlier (1959) for the 

 related El Salvador species T. gierloffi Hartmann. Such minute 

 striations, usually too fine to be drawn accurately to scale, can be 

 seen in several other species and genera. Triebelina is diagnosed by its 

 asymmetrical and robustly ornamented carapace as well as distinctive 

 soft-part morphology; the known species have smooth hinge elements. 



Neonesidea schulzi ifalikensis, new subspecies 



Figure Ae-m 

 "^Bairdia crosskeiana Brady, Brady, 1880, p. 58, pL 9: fig. 3a-c; 1890, p. 493. 



Type specimens. — Holotype male USNM 98549 (specimen no. 466) ; 

 paratype male USNM 98549 (specimen no. 465). 



Type locality.— If alik Atoll (USNM 98549), West Caroline 

 Islands. 



Diagnosis. — Carapace virtually indistinguishable from that of A''. 

 schulzi schulzi. Proportions of copulatory organ foreshortened, distal 

 lobe not visibly perforate, lamellar support of copulatory tube basally 

 thickened and distaUy pointed. 



