228 tolAllKS ON CONCTlOLOGY and MALAC'HOLOGY, 
3y well adapted to the habits aflife of Molluscous animals; there are 
numerous sheltered bays and inlets, with large tracts of level sand, 
and in other places, shelving rocks clothed in part with a variety of 
Alg®. It may, however, be questioned whether the geological 
formation of the coast is such as favours the growth of shells; so far 
as I can ascertain from the perusal of such recent works as I have 
met with, naturalists are but imperfectly acquainted with the pri¬ 
mary formafionofthe calcareous coverings of these animals: it is 
inown that the membrane which is called the Mantle of the animal, 
secretes a fluid more or less tenacious, which gradually hardens into 
the consistence of shell, and the manner in which it is deposited, lay¬ 
er by layer, has been minutely described by authors, yet it is not 
inown from whence the mineral substance is derived, or what change 
it undergoes to convert it into the material forming shell. It appears 
probable however, that soluble salts, or other combinations of lime 
existing in the water, arc absorbed into the body of the animal, and 
from thence by the proper ducts conveyed to the surface for the for¬ 
mation and nourishment of the shell. Should this be the case it might, 
cseteris paribus be expected that shells of the largest size would 
be found where calcareous rocks fringe the coast, and vice versa : 
here indeed an explanation of the difficulty seems at hand, for there 
are no rocks of a calcareous nature in this neighbourhood: on the 
other hand, it is difficult to account for the immense extent and rapid 
growth oftho Corallines which line our coast for many miles, and 
in the elegance of their forms, and variety of their species, almost 
vie with our land forests. 
This description of animal vegetation, if it may be so called, ap¬ 
pears also to obtain its nourishment by absorption from the sea water ? 
and I consider it not altogether unlikely, that this constant and active 
process maintained by the Corallines may interfere with the growth of 
shells in their immediate neighbourhood. One evident cause of the 
scarcity of many species, is, that the poorer Malays and Chinese use 
most kinds of shell fish as food, and search the shores for them with 
such diligence, that they have caused a dearth of such as are com¬ 
mon in less frequented parts of the coast. Among the group of 
small islands 30 or 40 miles south of Singapore, where a human 
habitation is rarely seen, the general character of the shells is 
similar to those of Singapore, but they are more abundant and of 
