ON GASTEROPODA. 339 
raised as the animal is younger, and consequently the last 
whorl is larger in proportion; the wmbilicus is more un- 
covered; the aperture is wider, the edge more trenchant, and 
the shell is thinner. Accordingly, when it is terminated, the 
last whorl comes out from the line of the spiral, and becomes 
falling, which renders the aperture more narrow. ‘These dif- 
ferences are important to be known, otherwise we might be 
liable to consider individuals of different ages as different 
species. We find also, in these animals, and especially in 
their shells, some anomalies. ‘Thus we find some that are 
entirely deft, that is, all the parts are reverted from right to 
left, and then the shell has its free edge at the left, and the 
columellary one at the right. We also find some in which 
‘that part of the body, which is in spiral, instead of being very 
compact, is twisted in a very loose manner, or merely a little 
recurved. ‘The shell then assumes the form of a sort of cork- 
screw, and is termed scalaria. ‘The cause of these irregulari- 
ties is unknown. 
The uses of the helices, or snails, are not very numerous. 
It appears, however, that the larger species, and especially 
the garden snails (H. pomatia, L.) serve for the aliment of 
man in many countries. ‘The Romans, according to Pliny, 
consumed great quantities of them ; and they must have been 
in great estimation for the table, since that author has thought 
it necessary to give, in his Natural History, the name of 
him who first thought of rearing these animals in sorts of 
parks, or depots, and fattening them with particular sub- 
stances. The best came from the island of Astypalza, one of 
the Cyclades, the smallest from Reate, in the Sabine terri- 
tory, and the largest from Illyria. The Romans also greatly 
esteemed the snails of Sicily, of the Balearic Isles, and of the 
Island of Caprea. They shut them up in sorts of warrens, and 
fattened them there with cooked meat, flour, &c. It was 
Fulvius Harpinus who first conceived the idea of this pre- 
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