416 
CRUSTACEA. 
.i ' 
The seventh and last section, the Notopoda, is formed of Crabs having the four or two posterior : 
legs inserted above the plane of the others, and seeming to be dorsal, and directed upwards. In those 5 
where they are not terminated by a sharp hook, the animal generally uses them to retain in its hold ; 
various marine productions, such as the valves of shells, sea-weeds, &c., with which it covers itself. 
The tail has seven joints in both sexes ; the majority have the abdomen bent beneath the breast, and 
the legs terminated by a short hook, and unfitted for swimming. 
Homola, Leach, have the carapax nearly square ; the antennae long ; the ocular peduncles long ; the claws of 
the males larger than the females, and the posterior pair of legs directed upwards. The outer foot-jaws are long 
and exposed [as in the Macrurd\. The type, H. spinifrons, Leach, is a native of the Mediterranean, and is the 
Hippocarcinus of Aldrovandus. 
Dorippe, Fab., has the four hind-legs elevated, as has also Dromia, Fab. 
Dynomene, Latr., has the carapax of the ordinary form, and the two hind legs alone elevated. 
Ranina, Lam., is a singular genus, differing from all other Brachyura in having the abdomen extended, [but 
not furnished at the end with an apparatus for swimming] ; and from the other Notopoda, in having the six 
intermediate legs dilated and natatorial. The carapax is of a reversed triangular form, the front much toothed. 
The species are exotic. 
[The Brachyurous Crustacea, here given as a single genus. Cancer, have, from the great number of 
species of which they consist, their large size, and facility of preservation, owing to their solid envelopes, 
attracted the attention of many recent authors. The Malacostraca Podopthalma Britannica, of 
Leach ; the Histoire Naturelle des Crustaces, by Milne Edwards ; the Fauna Japonica, of De Haan ; 
the Memoirs of Professor Bell, published in the Transactions of the Zoological Society, and by 
Mr. MacLeay, in Dr. Smith’s Illustrations of Southern Africa ; together with Polydore Roux’s elegant 
work upon the Crustacea of the Mediterranean, must he consulted by those who would desire to 
become acquainted with the singular forms and multitudinous genera established in this tribe of 
animals.] 
THE SECOND FAMILY OF DECAPODA,— 
Decapoda Macrura {Exochnata, Fabricius), — 
Is distinguished by having, at the extremity of the tail, on each side, appendages*, ordinarily forming a 
swimmeret or instrument for swimming, the tail itself being at least as long as the body, extended, 
exposed, and bent under only towards the posterior extremity. Its under-side generally presents, in 
both sexes, five pairs of false feet, each terminating in two 
plates or filaments. The tail is always composed of seven 
segments. The branchiae are formed of vesicular, bearded 
and villose pyramids, arranged, in many, either in two rows 
or in separate bundles. The antennae are generally long and 
exserted ; the ocular peduncles are mostly short. The external 
foot-jaws are generally narrow, long, and palpiform, and do 
not entirely hide the other [internal] parts of the mouth. The carapax is narrow and more elon- 
gate than in the Brachyura, and ordinarily terminated in front in a point. MM. Audouin and] 
Milne Edwards (to whom we must refer for particulars) have noticed that in the lobster {Astacus j 
marinus. Fab.), in addition to the two large lateral venous canals, there exists a third, lodged in the 
sternal cavity, in which respect the venous systems of the Macrura and Stomapoda agree. The Ma- i 
crura never [or but in a very few instances] quit the water, and with a very few exceptions they are 
all marine. 
Adopting the plan of Delper and Gronovius, the Macrura may be considered as forming but a single ; 
genus t, Astacus, which may be thus divided : — 
Fig. i.—Gebia stellata, Leach. 
• These appendages are composed of three pieces, namely, a base, 
(or support to the two others), articulating with the penultimate seg- 
ment ; the terminal segment generally forming with them a fan-like 
swimmeret ; but in the terminal species the appendages are replaced 
by filaments. The sub-abdominal false legs are formed on the same 
model, and vary in number, there being only three or four small 
pairs in the Anomala, and wanting in the males (except the anterior 
pair). In the Hermit Crabs they seem to exist only on one side. Gut I 
in the subsequent subgenera they are constantly larger, and there are ■ 
five pairs, supporting the eggs and being useful in swimming. In the 
section Anomala, the peduncle of the intermediate a tenna is pro-; 
portionably longer, and the two or four posterior feet smaller, thus j 
approaching the Brachyura. 
t The sections which we have proposed ought rather to form soj 
many genera, based upon those of Fabricius. 
if; -...Flj JT Aei Si. 
