114 18 



Ch. I cannot agree with Edg. Smith when he says ' that "The few ribs towards the 

 middle being duplicate, as stated by Reeve, is an individual rather than a specific 

 character;" in all the specimens from the Gulf of Siam the majority of the ribs in 

 the middle towards the hinder extremity are duplicate. As mentioned in connec- 

 tion with A. compktnata, Gh., I have unfortunately not been able to lake into full 

 consideration Lamy's work on the genus Area, as my investigations upon this genus 

 were ended when the work in question was published. 



Area (Barbatia) parva, Sow. 



Bgssoarca pari'a, Sovverby, Proc. Zool. Soc. London, 1833, p. 19. 

 Area * — — Reeve, Conchol. icon., II, Area. Sp. 119. 



— (Barbatia) parva, Reeve, Martini u. Chemnitz, Conchyl. Cabin., VIII, 2 Al)tli., p. 197, pi. 47. lig. 7. 



— — — SowERBY, Lamy, .lourn. de Conchyl., vol.55, 1907, p. 51. 



Barhalia attenuata, Dunker i. I. Museum Godeffroy. Catalog IV. 1869, p. 114 — Catalog V, 1874. p. 173. 



West coast of Koh Chang, 10 fathoms, mud (1). Koh Mak, sand coast ('/2). 

 Long. 15 — 21 mm. 



Distribution: — Persian Gulf, Djibouti, Gulf of Suez, Madagascar. — Tahiti, 

 Paumotu Isl., Ducie's Isl. 



Area (Barbatia) Siamensis, n. sp. 



{PI. 1, Figs. 16—17). 



This shell is rather thin and ventricose, oblong rectangular in outline, and 

 the posterior half is swollen from the umbones obliquely downwards towards the 

 posterior part of the ventral side. The valves are somewhat obliquely twisted, 

 and the left valve projects, having its lower edge below that of the right valve. 

 The anterior end is rounded and passes evenly into the ventral side; the 

 posterior end, which is much higher, is rather straightly truncate and slopes 

 obliquely downwards towards the ventral side, with which it makes a rounded 

 angle; the ventral side is somewhat compressed in the middle. The surface of the 

 valves is closely set with about 48 flattened, smooth, radiating ribs, which are 

 provided with a longitudinal furrow towards the anterior end. The interstices 

 between the ribs are narrower than the ribs. From the umbones and down to 

 the middle of the ventral side there is a depression of the valves. The upper 

 margin is straight and rises sharply towards the posterior end. The umbones 

 are situated in the anterior third of the shell. The area is very narrow and long. 

 The colour is white and the hinder margin of each valve is dark-coloured. The sur- 

 face is covered by a thin, brown epidermis which in the interstices between the 

 ribs is set with small scales or bristles. There are about 47 hinge-teeth. The 

 interior of the valves is white, and the outer ribs project beyond the margin so 

 that the latter becomes dentate. 



' Report on the zoolog, collections made during tlie voyage of H. M. S. "Alert," p. 110. 



