(iASTJiltOPOUA. MOLLUSCA. -Amphipekasidaj. 335 
only, and is not retractile, as is the case in the pre- 
\’ions siib-order. It varies in length and shape — in 
some being very long, but in a great many being 
short. The tentacles are' awl-shaped, far apart, and 
placed on the sides of the base of the rostrum. The 
eyes are situated on the outer side, or behind the base 
of these organs. The lingual membrane is often very 
long, extending a good way into the visceral cavitj^ of 
the animal, and the teeth are arranged upon it in seven 
series, 3, 1, 3. The foot of the animal varies in shape 
a good deal. In some genera we find it expanded, 
depressed, and formed for crawling, Plalypoda; in 
others it is roundish, truncate, or club-shaped, Pro- 
topoda; in a third set, it is compressed and adapted 
for leaping, Leptopoda; wliile in another series, it is 
fin-like, and furnished with a small sucker, Heteropodn. 
Family — AMPULLARIID^ {The Apple Snails). 
The animals of this family have the rostrum pro- 
duced, and the tentacles long and filiform. They have 
onl}'^ one well-developed gill, the left being nearly 
rudimentary, but the mantle has a large pulmonary 
sac on each side ; the foot is simple, and the oper- 
culum annular and regular; the shell is sub-globose, and 
covered with a hard, polished, olive-coloured epider- 
mis; the mouth is entire. 
The Apple Snails are fluviatile in their habits, and 
represent, in the ponds and rivers of the tropics, the 
Pond Snails of more temperate climates. They live 
chiefly in marshes, which are subject to periodical 
inundations, and are never found in rapid running 
streams. Where they do occur, it is generally in large 
numbers, for they are abundant, and cover a large 
space of country. They have the power of living a 
long time out of ■water when the marshes dry up. 
This faculty appears to have been first made known 
to us by M. Caillaud, who is well known as connected 
with the natural history of Egypt. After his return 
to France from a residence in Egypt, he had a number 
of sj)ecimens of Ampullaria ovata sent to him from 
the Nile. They were packed up with a number of 
other animals in a box filled with saw-dust. At the 
end of upwards of four months, upon opening the box, 
he found many of the objects in a state of putridity. 
The contents of the box he threw into a tub of water, 
and next morning he was surprised to find all the 
Ampullarise alive, and walking about apparently in a 
perfectly health}' state ! M. Deshayes, struck by this 
fact, and by the information he received from several 
other travellers that these animals buried themselves 
in the mud, and could support their existence for a 
length of time when the water was dried up and the 
mud hardened, examined several specimens with great 
care, and found in the branchial cavity a large open 
sac quite in the hinder part, and immediately above 
the base of the gills. He perceived also that this 
cavity was alwa3's full of water; and that after the 
Snail had ^withdrawn itself, and tightly closed the 
aperture by means of its close-fitting operculum, the 
water is retained in this sac, and the gill thereby kept 
in a moist and unshrivelled condition ; while, perhaps, 
as Dr. Johnston remarks, its contact with a living 
surface prevents the retained fluid running into putre- 
faction. The Apple Snails are oviparous ; the eggs 
are large, globular, and contained in capsules. These 
are disposed in masses, and attached to plants, &c. 
Specimens may be seen in the collection of mollusk 
eggs in the British Museum. The species are upwards 
of fifty in number, and are separated into several 
genera. The operculum, as well as the shape of the 
shell itself, affords good generic characters. In some 
this operculum is horny, with a shelly external coat, and 
the inner edge of the mouth of the shell is thickened, 
so as to afford some support to the thick shelly oper- 
culum. Such is the genus Pachystoma — Plate 1. 
fig. 1 — {Pachystoma solidum). Others have the oper 
culum simple and horny, and the edge of the shell thin. 
Such, for example, is the restricted genus Ampul- 
laria. The species of this group inhabit chiefly the 
rivers and lakes of South America and the West 
Indies. The South American Indians term them 
“Idol Shells,” and are. said to hold them in great 
veneration. 
Family — AMPHIPERASID.^ {Poached Eggs). 
The family of Poached eggs (the genus Ovulum 
of Lamarck ; family Amphiperasidee of Gray) is the 
second family of the Rostrifera. In this -family, and 
in the succeeding family of Cowries, CyprceidcR, the 
mantle of the animal, when adult, is expanded, and 
often reflexed over the shell, giving the surface a fine 
polished appearance. There is no operculum. The 
shells are involute, have a linear aperture, and a smooth 
inner, and toothed or crenated outer lip. When young, 
they are spirally striated, but when full grown, are 
covered with a smooth enamelled coat. The aperture 
in man}' of tlTe species is prolonged into a canal both 
in upper and lower extremities. The species are about 
thirty-six in number, and for the most part are dis- 
tributed through the warm seas of the AVest Indies, 
Mediterranean, China, and AVest America — one or 
two also occurring on our own coasts. They vary 
much in shape, and have thus given origin to several 
genera. Those which are ovate and ventricose, with 
a narrow aperture, the extremities not prolonged into 
a broad, inflexed, rounded, and crenulate outer lip, and 
long canals, form the genus Ovulum {Amphiperas). 
These are the true Poached eggs, and their shells are 
never ornamented with rich or varied colours, but are 
usually while, pink, pale violet, or yellow, without 
exhibiting any particular markings or pattern. Those 
in which the shell is fusiform, with an inflexed, 
toothed, outer lip, and the extremities of the aperture 
produced only into short canals, form the genus Cal- 
PURNUS. Cne of the species of ‘this genus is a native 
of the seas of the Philippine Islands, and the appear- 
ance of the animal and its habits have been well 
described by Mr. Adams. It is a very slow-moving 
and sluggish creature, he says, but exhibits a singu- 
larly beautiful and striking appearance under the calm 
shallow water, as it glides tranquilly along the bright 
sandy bottom. The head is pure, opaque white, with 
the exception of one large black spot placed in the 
centre of the forepart, which, with its large black eyes 
