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. 



Lticina iMijrteai seminula, Goui.d, Proc. Hostoii Soc. Nat. Hist., VIII, 18()1, p. 3(i. 



— (Cudakia) — Edg. Smith, Rep. Lamellibiancliiata of the Challenger Exped., p. 180, pi. 13, fig. 5. 



S. of Koh Samit, 20 fathoms, mud ('/s). 

 Long. 15 mm. 



Distribution: — Hong Kong Harbour; south of New Guinea. 

 Dall refers this and allied forms (L. pisum, Reeve, and others) to the sub- 

 genus Parvilucina, section BeUiicina. 



Diplodonta amboinensis, Sm. 



Diploiionla amboinensis, Edg. Smith, Report on the Lamellibiancliiata of the Challenger E,\p., 1885, p. 199, 

 pi. U, fig. 12. 



Gulf of Rayong, 7 — 10 fathoms, sand and mud (^'a). Between Koh Chuen and 

 Koh Chang, 15 fathoms, mud (■'Is). Koh Mak, sandy coast {'h). N. of Koh Kahdat, 

 4 — 5 fathoms, coarse sand (^/s). Koh Kahdat, 1 fathom, sand ('(a). Between Koh 

 Kut and Koh Kahdat (-/s). 



Long. 5 — 19 mm. 



Distribution: — Amboina ("Challenger"). 



This species is very closely related to Dipl. rotundata, Mont. 



Diplodonta ethima, Mel v. & Stand. 



Diplodonta ethima, Mki-vii.l and Standen, Jouin. Linn. Soc. Zoology, vol. 27, 1899, p. 197, pi. 11, fig. 17. 



Koh Kram, 30 fathoms (2). Gulf of Rayong, 7 — 10 fathoms, sand and mud ('/s). 

 Between Koh Mesan and Koh Chuen, 25 — 30 fathoms, stones and shells (V2). S. of 

 Koh Chuen, 30 fathoms, shells (^/a). Between Koh Chuen and Koh Chang, 15 fathoms, 

 mud (^'3). Off Tung Kaben, 6 fathoms, mud mixed with sand (1). Coa.st of Lem 

 Ngob, low tide (V2). Between Koh Kut and Koh Kahdat, 10 fathoms, shells C/2). 

 Koh Kahdat, 1 — 5 fathoms, sand and stones (^/s). S. of Koh Kahdat, 8—10 fathoms, 

 mud {^l-i). W. of Koh Kut, 30 fathoms, sand and mud ('/a). 



Long. 4 — 10 mm. (long. 10 mm., alt. 95 mm., crass. 65 mm). 



Distribution: — Singapore, low water (Sv. Gad), 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. 



