3$E MARKS ON CONCHO LOGY AND MALACHOLOGY, 237 
ae to be almost invisible. The shell has been found in running streams 
but more commonly in the brackish water of canals or ditches. 
The very numerous genus of 44 Cypraea” or the 44 Cowry” shell is 
too well known to require a formal description, the largest species 
found here is the 44 Cypraea tigris” which is prettily spotted with black, 
being shewy, it is frequently made into snuff boxes in England, 
the animals of several have been described and figured by authors. 
The mantle is so large as to cover all the shell, on the back of 
which there is often a longitudinal line which marks where its two 
folds meet: this membrane continually secretes an abundance of vis¬ 
cid fluid which lubricates the shell, and preserves the beautiful 
polish which has procured for them the name of porcelain shells. 
X shall only make particular mention of two kinds, the young or 
spawn of which I have been fortunate enough to obtain in their ear¬ 
liest stage of existence. 
The 44 Cvprsea olivacea” is the most abundant of the Singapore Cow¬ 
ries being found on most beaches under flat stones, it is of the size 
and much the colour of an olive except that the back is generally 
mottled with brown and the mouth somewhat yellow; the specimen 
which I found with the young attached, was fixed in the usual man¬ 
ner, to the lower surface of a stone, on raising it there was found 
adhering to it, a flat circular membrane broader than the shell, trans¬ 
parent, and dotted with minute grey spots like grains of sand, on 
placing the substance in a glass of sea water, numbers of the 
grains dropped out of the membraneous mass to the bottom of the 
glass and immediately assumed rapid and lively movements, some 
revolving in a rotatory manner, others alternately rising and sinking 
in the water or sporting over its surface. On a closer examination 
these grains were seen to be in reality shells, some hundreds in 
number, nearly transparent, having no perceptible columella and ap¬ 
parently consisting of a single coil or whorl, aperture round, breadth 
of the shell greater than the length, so that, when on a plain sur¬ 
face it rested on either end like a Planorbis or Nautilus, the animal 
effected these rapid movements by the alternate contraction and expan- 
sion of its foot which was broad and expanded and much larger than the 
shell, into which it seemed to have no power of withdrawing it. 
There is another small Cowry occasionally found on the coast, re¬ 
sembling in colour the C. adust-' 1 , hut not more than half the siz? 
