GASTROPODS. 
363 
exclusively holostomatous, that is, with uninterrupted apertures. Gastropteron, 
which typifies another family, is remarkable for the great lateral expansions, or 
epipodia, which are used by the animal in swimming. The gill lies exposed on 
the right side, the head-shield is truncate in front and pointed behind, and the 
mantle terminates behind in a slender, whip-like appendage. At one time this 
mollusc was supposed to be shell-less, but in reality an internal shell does exist; 
but, as it is only ^ of an inch in diameter, it may be easily overlooked. G. 
meckeli, of the Mediterranean, is of a vivid red colour, with 
a few white spots, and a pale or bluish border to the lobes. 
In the PliilinidcB, as typified by Philine, the shell is very 
thin, and wholly concealed beneath the mantle. In form 
it somewhat resembles Bulla, but has the aperture larger. 
P. aperta, a very common British species, lives in shallow 
water all round the coast, feeding upon foraminifera and 
even small sea-urchins. The animal is white, has a very Philine aperta (nat. size), 
large frontal-shield, but no tentacles -or eyes. It is provided, 
as in the case of Scaphander, with a powerful gizzard. The ova, which are very 
numerous, are deposited in a single series, in a long and loosely-twisted cord, 
enclosed within an ovoid, gelatinous capsule. 
The sea-hares (. Aplysiidce ), so called on account of a slight resemblance to a 
crouching hare, and not for their nimbleness of foot, are elongate creatures, with 
a long neck, distinct head, oral and dorsal tentacles, and furnished beneath the 
mantle with a shelly plate to protect the branchiae. The mouth is provided with 
sea-hare, Aplysia (nat. size). 
horny jaws, and the gizzard is armed with horny spines, which prepare the food 
for digestion. The sides have large thin lobes, which are either folded over the 
back, or used in swimming. Aplysia includes both animal- and vegetable-feeders, 
inhabiting shallow water in all parts of the world. In olden time there were 
many stories in vogue respecting the poisonous nature of the sea-hare, but it has 
been shown to be harmless. It has the faculty of emitting a nauseous smell; and 
a beautiful purple fluid is discharged from glands in the edge and inner surface 
of the mantle. The species illustrated (A. depilans ) occurs on the coasts of France 
