The Journal of the Indian Archipelago. 269 



supposed to be a Gasteropod, though this is rather doubtful, as the 

 shell is said to be generally found imbedded in coral or madrepore : it 

 is probable that this point might be satisfactorily settled by a careful 

 examination of the above locality. Among other interesting dis- 

 coveries lately made on that part of the coast, is a layer or stratum 

 of grey limestone, of considerable extent, composed almost entirely 

 of petrified shells. I have been fortunate enough to obtain a speci- 

 men for examination which contains three distinct species, apparently 

 freshwater shells ; two of them I have never seen recent here, but 

 the third closely resembles a small Melania common here in stagnant 

 ditches, their size, number of whorls, and general shape are the 

 same, and they have both deep longitudinal striae or furrows ; some 

 of the shells were crystaline and amber coloured, though the material 

 uniting them was of an uniform grey colour, both substances however 

 were soluble in hydrochloric acid. 



" Of the numerous class of shells inhabiting the interior of madre- 

 pores, wood, and stone, there is a species allied to " Pholas" which 

 I cannot find described in any English work, though it seems to an- 

 swer the description of the Genus Jounannetia of M. Des Moulins in 

 a work entitled ' Manuel des Mollusques par M. Sander Rang/ the 

 shell is white, rather less than a musket ball, and nearly as globular 

 in form, with a slight caudiform appendage at one end, striated 

 obliquely and having accessory pieces, the consistence of the shell 

 more resembles that of the bivalve of the ( Teredo' than a Pholas ; 

 and M. Des Moulins considers it to hold a place between these two 

 genera. The specimens I have met with were in the interior of 

 rolled masses of f madrepore,' and were evidently old, as none con- 

 tained the animal alive or dead. The c Lima' or the c file shell,' 

 of which several species are found in the Straits, much resembles the 

 Genus f Pecten' or ' Scallop shell,' which is well-known to possess 

 greater power of locomotion than most bivalves. This power is 

 possessed even in a greater degree by the Lima. When in the water 

 its movements are graceful, the two valves being used as fins, by means 

 of which it swims with considerable rapidity, guiding itself by its 

 numerous tentacula which are frequently of an orange colour, and 

 arranged not unlike the petals of a flower, the shell is less eared than 

 the Scallop, and generally white, the valves do not entirely close. 



