192 CRUSTACEA EUCARIDA — DECAPODA chap. 



formed bj a sharply-pointed rostrum. There are two chief series, 

 the one comprising the Spider-crabs, with much elongated 

 walking legs, e.g. the huge 3Iaia squinado of European seas, the 

 yet more enormous Macroclieira Icilinpfcri 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 Inachus, Hyas, and Ste^iorliTjiichvs, which 

 are so connnon in moderate depths off' the English coasts. The 

 other series is represented by genera like Zamhrus (Fig. 133), 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, etc., 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 Part]ienoj)e investigatoris, one of the 

 short-legged Oxyrhyncha, the whole of whose dorsal surface is 

 wonderfully sculptured to resemble a piece of the old corroded 

 coral among which it lives. 



But besides this, the long-legged forms, such as Inachus, 

 Hyas, etc., 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 beeii 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 Enccpludoides armstrongi (Fig. 132), dredged by Alcock 

 from below the 100-fathoni line in the Indian Ocean, which has 



^ Natxiralist in Indian Seas, 1902. 



