192 CRUSTACEA——EUCARIDA—DECAPODA CHAP. 
formed by a sharply-pointed rostrum. There are two chief series, 
the one comprising the Spider-crabs, with much elongated 
walking legs, e.g. the huge Maia squinado of European seas, the 
yet more enormous Macrocheira kimpferi from Japan, supposed to 
be the largest Crustacean in existence, and sometimes spanning 
from outstretched chela to chela as much as eleven feet, and the 
smaller forms, such as Jnachus, Hyas, and Stenorhynchus, which 
are so common in moderate depths off the English coasts. The 
other series is represented by genera lke Lambrus (Fig. 153), in 
which the legs are not much elongated, but the chelipedes are 
enormous. 
The Spider-crabs do not burrow, and their respiratory 
mechanism is simple; but since they are forms that clamber 
about among weeds, ete., upon the sea-bottom, they often show 
remarkable protective resemblances to their surroundings, which 
are not found in the burrowing Cyclometopa. Alcock ' gives a 
good account and figure of Parthenope investigatoris, one of the 
short-legged Oxyrhyncha, the whole of whose dorsal surface is 
wonderfully sculptured to resemble a piece of the old correded 
coral among which it lives. 
But besides this, the long-legged forms, such as Jnachus, 
Hyas, ete., have the habit of planting out Zoophytes, Sponges, 
and Algae upon their spiny carapaces, so that they literally 
become part and parcel of the organic surroundings among which 
they live. It may, perhaps, be wondered what are the enemies 
which these armoured Crustacea fear. Predaceous fish, such as 
the Cod, devour large quantities of Crabs, which are often found 
in their stomachs; and Octopuses of all sorts live specially upon 
Crabs, which they first of all paralyse by injecting them with 
the secretion of poison-glands situated in their mouth. The 
poison has been recently found by Dr. Martin Henze at Naples 
to be an alkaloid, minute quantities of which, when injected into 
a Crab, completely paralyse it. When the Crab is rendered 
helpless the Octopus cuts out a hole in the carapace with its 
beak, and sucks all the internal organs, and then leaves the 
empty shell. 
Many of the Oxyrhyncha are found in the abysses; among 
them are Encephaloides armstrongi (Fig. 152), dredged by Alcock 
from below the 100-fathom line in the Indian Ocean, which has 
1 Naturalist in Indian Seas, 1902, 
