352 SYNOPTIC COLLECTION. 



and is covered with a thick coating of hairs which in 

 color and texture resemble the fibers of the sponge. In 

 this way, whether by conscious mimicry or by an instinc- 

 tive adaptive power, the crab is perfectly protected. 



Even the naked jaws of the claws are not hard or limy 

 but so soft that they crush in the fingers. According 

 to Bell 1 the young have the carapace entirely covered 

 with a sponge which also conceals the two hinder pairs 

 of legs as these are pushed above the others and are 

 closely pressed against the back. The function of the 

 legs that have been pushed out of their natural position 

 is to assist in holding the sponge on the crab's back, and 

 consequently sharp hooks have developed at their ends. 



The plump, rounded appearance of the front of the 

 cephalothorax which extends forward beyond the sponge, 

 with the deep-set eyes in their circular sockets, gives an 

 almost cat-like expression to the crab which is amusing. 



The little Porcellana ocellata (No. 862) is interesting 

 for the reason that its telson bears a pair of appendages. 

 The telson itself is small and pointed ; the appendages 

 are fastened to it on its sides and also united to each 

 other in the median line behind the point of the telson. 

 These appendages with those of the sixth abdominal seg- 

 ment, together with the broad, well-developed abdomen 

 which turns under the cephalothorax, enable this little 

 animal to swim; hence the popular name of "crab-lob- 

 ster." But, although it can swim on occasion, it prefers 

 to stay under stones or in narrow crevices, and the struc- 

 ture of its body is well adapted to such an environment, 

 for both the cephalothorax and abdomen and also the 

 appendages give one the impression that Porcellana has 

 been pressed out flat. 



Lithodes (No. 863, placed towards the back of the Sec- 

 tion) is one of the giant crabs of the group represented 

 by the hermit crab. Armed with spines and knobs it is 



1 Brit. Stalk-eyed Crustacea, 1853, p. 371. 



