114 The Official Guide to the 
to rocks in the Tidal Zone. Various descriptions, 
named from the form of the shell, are known as 
“Duck Bill,” ‘ Bonnet,” ‘‘Cup-and-Saucer,” and 
“Sandal” Limpets. One species, Patella vuleata, 
is Common on our coast. 
Case Il. 
The C%zfons are singular armoured Sea-Slugs. The — 
plates, eight in number, being fixed transversely on 
the back of the animal like the bands of the Armadillo ; 
they move on a broad foot or base, and have the 
power to roll themselves up like a Hedgehog. 
The Land and Freshwater Air-breathing Mollusca 
(Pulmonata), next in order, the first family of which, 
HELICID2, contains many individuals with which we 
are familiar, such as the common Garden Snail. It 
sometimes, though rarely happens, that the whorls of 
these shells are reversed, such specimens will be- 
noticed in the collections. As many of these shells 
will be referred to when we come to the British 
section, it will only be necessary here to mention 
some few of the more remarkable examples. 
The extensive genus, Au/imus, contains some very 
fine sub-tropical snails ; the shell of &. ovatus, a South 
American species, being as much as six inches long ; 
but even this is exceeded by the great African 
ACHATIN#, or Agate shells, one of which, 4. d¢carinata, — 
is the largest of all known land shells, and attains a 
length of eight inches ; examples of this fine species, 
with the thick calcareous shelled egg, will be seen. 4. 
zebra is also a fine species, very beautifully marked. 
A fine collection of Helices, many of them from 
the Philippine Islands, will be found in the Taylgy 
collection. 
