The Journal of the Indian Archipelago. 271 



" In Swainson's Malachology there is a species figured as an extra- 

 ordinary animal, much larger than the shell it is supposed to in- 

 habit, one of the species found here presents the same appearance in 

 a remarkable degree ; and the phenomenon is caused in the fol- 

 lowing manner ; the interior of the foot of the animal is of a loose 

 cellular texture, which it has the power of distending with water so 

 as to be more than three times the bulk of the shell, but on the 

 approach of danger it can instantly reject the water, assume its 

 natural size, and retreat into its shell, closing after it the operculum, 

 which being of stony hardness, secures it from the attack of ordinary 

 foes. This mechanism doubtless assists the progress of the animal 

 through sand, in which it frequently burrows. 



" The Cerithium lineolatum of Gray, has been already alluded to : 

 there are two shells of this genus, neither of which I have seen des- 

 cribed, though I observed one of them named as above in a collec- 

 tion of the land and freshwater shells of Penang, made by Dr. 

 Cantor, the shell so designated is about an inch and a half in length, 

 thin and fragile, of a brown colour, with obscure transverse bands 

 of a lighter hue, aperture more rounded than is usual in the genus 

 Cerithium, spire always truncated in the full grown shell, head and 

 anterior part of the animal bright-red, like coral : the other species, 

 which I have more particularly observed in Singapore, has rather a 

 larger shell, thinner and more fragile than the other, and of a darker 

 colour, the animal is brown, or nearly black, and like the former, the 

 spire of the full grown shell is always decollated ; young specimens 

 of the shell have perfect, sharp-pointed spires, and the convoluted 

 extremity of the animal then entirely fills the spiral part of the shell, 

 but as the animal increases in size, its posterior extremity becomes 

 more blunted and gradually retreats towards the anterior part of the 

 shell, and as it successively abandons each turn of the spire, it 

 throws out a viscid secretion, which forms a hard, shelly, partition be- 

 tween its new situation and the disused extremity of the spire, which, 

 being deprived of its usual nourishment, soon becomes worn into 

 holes and finally drops off : thus the shell, when arrived at maturity, 

 has always the appearance of being imperfect. The habits of the 

 animal are mixed and peculiar ; sometimes it may be seen in a half 

 torpid state, the operculum firmly closed, suspended by a glistening 



