288 
Stomapoda. CRUSTACEA. Ajiphipoda. 
victim, clothing themselves with its spoils. They run 
about with great rapidity, and when seized draw them- 
selves into the shell with a sudden snap, close the aper- 
ture with their stout claws, and resist strongly all at- 
tempts to pull them out. When young they may be 
found inhabiting small shells, such as the periwinkle, 
&c., but as the}' increase in size they take possession 
of the large whelk or buccinum. 
Order II.— STOMAPODA {Sea-Mantea). 
The Stomapoda are distinguished from the Decapoda 
by their not possessing internal branchiae or gills. These 
organs when present are external, and generally spring 
from the basal joint of the abdominal false feet. Some- 
times they are fixed at the base of the thoracic feet, and 
are suspended under the thorax. The carapace varies 
in form and size, sometimes covering the whole thorax, 
or at others only part. The abdomen varies much in 
appearance also. In general it resembles that part of 
the body in tlie Macroura, and terminates in a caudal 
fin, which fits them for swimming. The feet are seven 
or eight pairs, and in most of the species are placed 
near the mouth, or are folded upon it, hence the name. 
In some genera of this order the thoracic feet are slen- 
der, resemble each other in form, and are all adapted 
for swimming. In others, the first pair are large and 
prehensile, and the three succeeding pairs are also claw- 
shaped and formed for prehension. 
Mysis. — Amongst those of the first group we may 
mention the genus Mysis, the species of which are 
known by the name of the Opossum shrimps. They 
derive this name from their carrying their eggs and 
young in a pouch beneath the thorax and between the 
thoracic legs. The species are small and have the 
body narrow and elongated, like the shrimps. They 
are found in vast numbers, especially in the northern 
seas, where they constitute a large portion of the food 
of the whale, and are luminous at night. 
In this group we have also the curious crustaceans 
belonging to the genus Phyllosoma, the body of which 
is transparent and so completely flattened, that it is 
difficult to understand how the viscera have room to 
play. 
In the second group we may mention the genua 
Squilla. 
THE MANTIS CRAB (Squilla 
Desmarestii — fig. 186) is about 
seven inches in length. Its 
carapace only covers the an- 
terior half of the thorax, the 
hinder being formed of I’ings 
like those of the abdomen. It 
is provided with enormous 
claws, terminating in a sharp 
hook; the last joint furnished 
with six sharp projecting 
spines, and the preceding joint 
with three, and so hollowed as 
to render this claw a most effi- 
cient instrument of prehension. 
They bear a considerable re- 
semblance to the fore legs of 
tlie Orthopterous genus of in- 
sects, Mantis; hence the popu- 
lar name applied to the species 
of this gemis. This species is 
a native of the seas of Europe, but the greater numbei 
are inhabitants of tropical seas. 
Fig. 180. 
Sea Mantis, 
or Mantis Crab. 
Section II. — SESSILE-EYED CRUSTACEA (Edriophthalma). 
The Sessile-eyed Crustaceans are distinguished from 
the Stalk-eyed, or Podophihalma, by their branchiae, 
or gills, not being organs specially formed for the pur- 
pose of respiration, but constituting a part of the organs 
of motion, their structure being peculiarly adapted to 
serve that end ; and by their eyes not being placed on 
foot-stalks, but being sessile and immovable. They 
have no thoracic carapace; but the thorax and abdo- 
men are composed of a series of rings or joints, sepa- 
rate from each other and movable. The head is 
distinct from the thorax. 
They are divided into three orders — Ampiiipoda, 
Lasmodipoda, and Isopoda. 
Order I.— THE AMPHIPODS {Amphipoda). 
The Amphipods have their branebim or gills in the 
form of large membranous vesicles placed at the base 
of the feet, on their inner side. The thorax is gene- 
rally divided into seven movable rings, and the 
thoracic, or true feet, are seven pairs. The abdomen 
is large and well developed, and the members, or false 
swimming feet attached to it, are elongated, narrow, 
and fringed with hairs. The three hinder pairs are 
bent backwards, and, along with the terminal portion 
of the abdomen, form a sort of fin, which serves the 
animal for swimming or leaping. The females carry 
their eggs under tlie tliorax, between certain scales or 
vesicles, which form a kind of pouch. In this position 
they are hatched, and the young remain attached to 
the legs, or other parts of the body of the parents, until 
they gain sufficient strength to swim and take care of 
themselves. The order contains a considerable num- 
ber of species, all of small size — some are paiasitical, 
living attached to fishes, and in Medusae or Acalephae. 
Such are the species of the genus Phronima, one or 
two of which are European, and are found inhabiting 
the interior of a gelatinous, transparent, bell-like bag, 
open at both ends, and formed probably of the body of 
a Beroe. Others are free and very active, some living 
in the sand of the sea-shore, others in the sea or fresh- 
water. 
Talitrus. — The species of this genus are well 
known by the name of Sandhoppers, or Sea-fleas. 
1 
