262 
CRUST A CEANS 
not upon the breast-plate of the cephalothorax. Moreover, as in the Dorippidce of 
the preceding tribe, the last or last two pairs of legs are shorter that the rest, and 
dorsally placed, as shown in the illustration of the common Drontia vulgaris. 
The crab uses these limbs to hold foreign bodies like sponges and shells beneath 
which it thus lies concealed. 
Long-Tailed Group,— Suborder Macrura. 
This suborder, comprising the lobsters, hermit-crabs, prawns, and shrimps, is 
distinguished by having the abdomen or tail usually of large size, and constituting 
a powerful flapper for swimming, in which function it is assisted by the 
enlargement of the appendages of its last segment to form with the telson a 
powerful tail-fin. The external maxillipedes are slender and leg-like, and the 
antennae usually longer than the body. The first tribe, Anomura, contains forms 
which typically have a symmetrical tail. With these were originally classified the 
anomalous crabs, and there is no doubt that some of the species bear a striking 
resemblance to the latter. This is shown in the illustration of the broad-clawed 
porcelain-crab ( Porcellana platycheles), which frequents 
rocks and seaweed at low water. It may be distinguished 
from the true crabs by its long antennae, the presence 
of a tail-fin, and the slender unflattened external maxil¬ 
lipedes. The most familiar members are the hermit- 
crabs, which abound in all seas, and are represented by 
several British species. In the typical forms, the integu¬ 
ment of the abdomen is soft; and, aware of its defenceless¬ 
ness, the hermit-crab invariably thrusts itself for protection 
into some empty shell, which it subsequently never 
willingly quits, save for the purpose of changing its abode for a larger one, when 
compelled by the exigencies of growth. It is not an uncommon thing to find shells 
containing a hermit-crab surmounted by a large anemone. The advantage to the 
crab of this association is considerable, for anemones are so distasteful that no fish 
will bite at them twice, and consequently a fish that would, under ordinary circum¬ 
stances, greedily swallow a hermit-crab, shell and all, will not so much as sniff at it if 
protected by an anemone. One of the commonest deep-water British hermit-crabs, 
Eupagurus prideauxi, is invariably found associated with an anemone, but the 
latter adheres to the lower surface of the shell in such a manner that its mouth 
and tentacles are situated immediately below the forepart of the crab’s body. It 
is thus able to share in the meals that the crab procures for itself, and the com¬ 
panionship) is consequently mutually beneficial to the two. An advantage conferred 
upon the crab by the presence of the anemone results from the fact that the latter 
gradually absorbs the shell in which the former is lodged, so that there is no 
occasion for it to change its abode with growth, the soft tissues of the polyp 
offering; no resistance to the crab’s increase in size. Certain hermit-crabs have 
forsaken the sea as a permanent abode, and spend the greater part of their lives on 
land. For instance, the genus Cenobita, which occurs both in the West Indies and 
India, may be met with in forests far from the coast. The best known of these 
BROAD-CLAWED PORCELAIN 
crab (nat. size). 
