184 88 



Montacuta (Tellimya) rudis n. sp. 



(PI. III, Figs. 33-34). 



This shell, which is oblong-ovate, is, especially in the anterior half, .somewhat 

 ventricose; it is white and rather thin. Anteriorly the shell is truncated, but 

 posteriorly it is pointed. The ventral side is straight; across the middle from the 

 umbones to the ventral margin the valves are somewhat depressed. The umbones 

 are situated in the anterior half of the shell, the apices are glossy, smooth and 

 pointed. Upon the surface, which is covered with a yellowish epidermis, the rough 

 and coarse concentric lines of growth may be seen; in addition to these are distri- 

 buted, over the whole surface, numerous fine or coarse grains and tubercles which 

 make the valve-surface peculiarly rough and uneven. The interior of the valves 

 is glossy, the left valve has in it, separated from the upper margin by a groove, 

 two diverging, triangular, compressed, acute cardinal teeth, between which are 

 placed the ligament and the ossicle; these fit into a triangular pit just below the 

 apex of the right valve; close to this pit and directly upon the upper margin there 

 is on both sides in the right valve an oblong lateral fold, which fits into the 

 corresponding groove above the cardinal teeth of the left valve. The muscle im- 

 pressions are large and very conspicuous. 



Long. 75 mm., alt. 5 mm., crass. 3 mm. 



The north side of Koh Chang, 12 fathoms, in old coral blocks (1). 



The peculiar surface is characteristic of this species, which lives in holes in 

 coral blocks and which therefore, as is the case with all the forms which are found 

 in such localities, is subject to changes in form according to the locality which it 

 may chance to inhabit. 



Lepton sp. 



A single, somewhat damaged, left valve of a Lepton was taken in the sound 

 of Koh Chang, in 3 — 5 fathoms, on a soft muddy bottom; it should be placed near 

 to L. irigonale, Tait, but differs from it. In the British Museum there is a specimen 

 of an undetermined Lepton from Port Lincoln which exactly agrees with my shell 

 from the Gulf of Siam. 



Fam. Galeommidae. 



Galeomma angusta, Desh. 



Galeomina ungusla, De.shayes, Proc. Zoo]. Soc. London, XXIII, 185,5, p. 170, No. 7. 



— — — SowKRBY, Tliesaurus Conchy)., Ill, p. 174, No. 8, pi. 234, fig. 10. 



— — — SowKHBY in Reeve, Concliol. icon., vol. 19, Galeomma, Sp. 3. 



Coast of Lem Ngob, low tide, stones (150 specimens). Gulf at the south end 

 of Koh Chang (7). Koh Chang, very low tide, stones (5). North end of Koh Chang 

 1 fathom, old coral blocks (2). 



