1916. | H. B. Preston: Andaman Marine Mollusca. 92 
umbilicus, in its coarser revolving striae and more cylindrical and 
truncate form. 
Alt. 5°25, diam. 2 mm. 
Aperture: alt. 5°25, diam. °25 mm. 
Hab.—Port Blair, Andaman Is. (S. Kemp). 
Family APLUSTRIDAE. 
Micromelo undatum (Bruguiére). 
Brug., Encycl. Méth., 1, p. 380 (as Bulla); Tryon, Man. Conch., Vol. 
XV, p. 392, pl. lix, figs. 20-24. 
Off Ross I., in 2-10 fathoms, on a bottom of sand, stones and 
coral. 
A single very brightly coloured example which is inseparable 
from the West Indian shells in the British Museum. 
Class PELECYPODA. 
Order TETRABRANCHIA. 
Sub-order MyTILAcEA. 
Family MyTILIDAr. 
Mytilus curvatus, Dunker. 
Proc. Zool. Soc., 1856, p. 361; Reeve, Conch. Icon., sp. 53, pl. xi, fig. 53. 
Brigade Creek, in 2-5 fathoms, on a bottom composed of 
decaying vegetation. 
Sub-order ARCACEA. 
Family ARCIDAE. 
Arca (Anadena) holoserica, Reeve. 
Proc. Zool. Soc:, 1844, p. 39 (as Arca) ; Reeve, Conch. [con., sp. 11, 
pl. i. 
A young specimen from Semiramis Bay, in 2-6 fathoms, in 
fine mud. 
Family NUCULIDAE. 
Nucula semiramisensis, sp. n. 
(Figs. 9, 94, 90.) 
Shell tumid, ovately rhomboidal, covered with a thin, pale 
reddish-brown periostracum, polished, shining, minutely, obsolete- 
ly, transversely striate, and marked with concentric growth lines; 
umbones pearly, not prominent; dorsal margin arched in the me- 
dian part, anteriorly sinuous, posteriorly bulging; ventral mar- 
gin rounded ; anterior side sharply angled above, obliquely sloping 
below ; posterior side rather slightly produced, sharply rounded ; 
hinge plate bearing on right valve five erect, sharp-pointed, 
