174 78 
by the absence of the strong depression down the hinder side of the valves and 
the feebler one in front, and by some of its radiating ribs — which are considerably 
stronger than the concentric ribs — dividing in the middle of the valves. 
Lucina (Phacoides) seminula, Gould. 
Lucina |(Myrtea\ seminula, GouLp, Proc. Boston Soc. Nat. Hist., VIII, 1861, p. 36. 
-  (Codakia) — Epc. Smiru, Rep. Lamellibranchiata of the Challenger Exped., p. 180, pl. 18, fig. 5. 
S. of Koh Samit, 20 fathoms, mud ('/2). 
Long. 1:55 mm. 
Distribution: — Hong Kong Harbour; south of New Guinea. 
Dau refers this and allied forms (L. pisum, Reeve, and others) to the sub- 
genus Parvilucina, section Bellucina. 
Diplodonta amboinensis, Sm. 
Diplodonta amboinensis, Epc. SMirn, Report on the Lamellibranchiata of the Challenger Exp., 1885, p. 199, 
pl. 14, fig. 12. 
Gulf of Rayong, 7—10 fathoms, sand and mud (1/2). Between Koh Chuen and 
Koh Chang, 15 fathoms, mud (7/2). Koh Mak, sandy coast (*/2). N. of Koh Kahdat, 
4—5 fathoms, coarse sand (*/2). Koh Kahdat, 1 fathom, sand (*/2). Between Koh 
Kut and Koh Kahdat (*/2). 
Long. 5—19 mm. 
Distribution: — Amboina (“Challenger’’). 
This species is very closely related to Dipl. rotundata, Mont. 
Diplodonta ethima, Mely. & Stand. 
Diplodonta elhima, Meiyiti and Sranpen, Journ. Linn. Soc. Zoology, vol. 27, 1899, p. 197, pl. 11, fig. 17. 
Koh Kram, 30 fathoms (2). Gulf of Rayong, 7—10 fathoms, sand and mud (*/:). 
Between Koh Mesan and Koh Chuen, 25—30 fathoms, stones and shells (‘/2). S. of 
Koh Chuen, 30 fathoms, shells (*/2). Between Koh Chuen and Koh Chang, 15 fathoms, 
mud (!/2). Off Tung Kaben, 6 fathoms, mud mixed with sand (1). Coast of Lem 
Ngvb, low tide (‘/z). Between Koh Kut and Koh Kahdat, 10 fathoms, shells (1*/2). 
Koh Kahdat, 1—5 fathoms, sand and stones (*/2). S. of Koh Kahdat, 8—10 fathoms, 
mud (*/2). W. of Koh Kut, 30 fathoms, sand and mud (12). 
Long. 4—10 mm. (long. 10 mm., alt. 95 mm., crass. 6°5 mm.). 
Distribution: — Singapore, low water (Sv. Gap), Torres Strait (MELVILL & 
STANDEN). 
The specimens from the Gulf of Siam vary rather considerably in form, and 
it will doubtless, at some time, be proved, when the Diplodonta-group has been 
critically investigated — which it greatly needs — that D. ethima has a wider 
distribution; it hides itself perhaps under other names. 
