172 76 



down the anterior side and one broader radiating depression down the posterior 

 side. It is almost circidar in outline, l)ut the posterior end is rather straightly 

 truncated. Tlie surface is covered with numerous close-set, regularly-arranged, fine, 

 slender liræ, which towards the lunule and hinder dorsal slope are more elevated. 

 The lunule is rattier deep and large, cordiform, smooth. The area is long and 

 narrow. The beaks are small, sharp, well-curved over the lunule. The valves are 

 covered (in quite fresh individuals) with an extremely thin epidermis, which under 

 tlie lens exhibits a few fine radiating lines. In both valves the lateral teeth are 

 well-developed, the posterior being the smaller, and the cardinal teeth are obsolete; 

 the internal ligament is in a groove just within the dorsal margin. The interior 

 of the valves is of a dull white colour and under the lens is seen to have fine, 

 faint, radiating lines. 



Long. 7'5 mm., alt. 8 mm., crass. 5 mm. 



The strand off the mangrove at the station on Koh Chang (54). 



The peculiar depressions down the anterior side are characteristic of this 

 species. The shell varies rather considerably in form; especially in older specimens 

 it has a tendency to be drawn obliquely towards the anterior end, so that the 

 umbones may even be situated far back in the hinder half of the shell, while in 

 other individuals they are situated in the middle of the length of the shell. I have 

 named this new species after Mr. W. H. Dall of Washington to whom malacological 

 science owes so many valuable papers, and who has also revised the genus Lucina. 



Lucina (Phacoides) pisum, Reeve. 



Lucina pisnm, Hi;i;vk, Conchol. icon., VI, 1850, Lucina, Sp. (56 (non Lucina pisum, Philippi' = Divaricclla 

 perparvula, Dall -). 

 — iCodakia) pisum, Reeve, Edg. Smith, Laraellibrancliiata of the Challenger E.xped., p. 181. 

 Parinlucina eucosniia, Dall, Synopsis of the Lucinacea, 1901, p. 806. 



Between Koh Mesan and Cape Liant, 5—9 fathoms, sand ('/a)- Between Koh 

 Riot and Koh Mesan, 3—5 fathoms, sand (-/a). S. of Koh Chuen, soft clay and 

 mud ('-'/a). Gulf of Rayong, 7 — 10 fathoms, sand, mud, and shells ('/-•). S. of Koh 

 Samit, 14—20 fathoms, mud (1 + -/a). Off Tung Kaben, 6 fathoms, mud mixed 

 with sand ('/a). Koh Chang, between stones, very low tide (1). West coast of Koh 

 Chang, 10 fathoms, mud ('/s). N. of Koh Kahdat, 4—5 fathoms, coarse sand ('/li). 

 Koh Kahdal, on the strand (about ^""/s specimens). S. of Koh Kahdat, 8—10 fathoms, 

 mud ("li). Between Koh Kul and Koh Kahdat, 10 fathoms, shells (■"•/:,'). W. of Koh 

 Kut, 18 fathoms, mud (9). 



Long. 2 — 6 mm. 



Distribution:— Singapore (Cuming; Sv. Gad, 2— 3 fathoms). Mergui Isis. 

 (E.V.Martens), Madras (Melvill & Standen), Gulf of Manaar (Thurston). — S. of 

 New Guinea ("Challenger"), Port Essington (Brit. Mus.). 



' Abbild, u. Besehr. neuer od. wen. gek. Conchyl., Ill, 1850, p. 105. 

 - Synopsis of the Lucinacea. Wash. 1901, p. 815. 



