230 REMARKS ON CONCIIOLOGY AND MALAGHOLOG1** 
ra, Fissurella grseca, Area tetragona, Natica castanea, and a species 
closely resembling Trivia europea. 
It has been already observed that the poorer natives have fre¬ 
quent recourse to shell fish as food, a few kinds however, are es¬ 
teemed delicacies and are frequently exposed for sale in the mar¬ 
ket; of these may be enumerated Area granosa, (the shell of which 
somewhat resembles our common cockle) Corbicula regia or Cy- 
rena ol Lamarck, Cerithium lineolatum of Gray, and Voluta melo, 
though the latter is not always procurable. Among the eatable 
shell fish, the Oyster must not be omitted, though it is for the 
most part lightly esteemed by the natives, who generally prefer such 
kinds as have a stronger taste. A variety of Oysters may be found 
here but all are not eatable, two species in particular are of consider¬ 
able size, and excellent flavour, though found in very different loca¬ 
lities. I he one kind is abundant at Pedro Branca, a large rock at 
the entrance to the China Seas where they are exposed to rapid cur¬ 
rents and stormy waves; here they are invariably found strongly ad¬ 
herent to the rock by the surface of the lower valve. The other kind 
is procured fioin the mouth of the Moar river between Malacca and 
Singapore. These being comparatively safe from the effects of storms 
and currents are never fixed to rocks but lie loose in the mud, in 
beds of considerable extent. Although Oysters are so numerous in 
both these places, it is rare to find any other species of shell in their 
immediate vicinity, a circumstance that has been remarked of Oys¬ 
ter beds in England and other places. 
Without at all assenting to Lamarck’s theory of a Transmutation 
of Species it must be allowed that the discrimination between spe¬ 
cies and varieties among shells is extremely perplexing, the shades 
of difference between one species and another often appear less 
than between two varieties of the same species, the marks of distinc¬ 
tion are often so modified by various causes, as difference in loca¬ 
lity, change of food. &c, that uniformity of colour, size or even 
shape, when taken separately, are no safe guides, and unfortunately 
they are not always found combined. Blumcnbach wisely observes 
that w no general rule can be laid down for determining the dis¬ 
tinctness of species, as there is no particular class of characters 
which can serve as a criterion.” 
This variable tendency docs not prevail in all shells, though 
