78 A Guide to the Zoological Collections in the 



3rd Family, Cenobitidse. — These differ from the Paguridse 

 chiefly in having larger antennules. Several of the species 

 are terrestrial. The family is represented by specimens 

 of Cenobita and Birgus. Of Cenobita^ which much resem- 

 bles Pagiiriis^ several species are found swarming in the 

 jungles of the Andaman and Laccadive Islands. Birgus 

 is a gigantic land Hermit-crab which does not take 

 possession of a shell, and has the upper surface of the 

 abdomen not soft as in other Paguridea, but covered 

 by hard calcareo-chitinous plates. The lower unexposed 

 surface of the abdomen is, however, soft. In the Indian 

 region Birgus is known to occur only in the jungles of 

 the Httle island of South Sentinel in the Andaman group. 

 In Birgus observe that the fifth pair of legs is tucked up 

 beneath the carapace within the breathing chamber. Ob- 

 serve also that the female is furnished with a single bilobed 

 hairy leg on one side of three of its abdominal segments : 

 these legs are found in the female only, and are used for 

 carrying the eggs in the breeding season. 



The gills in Birgus are present, but are much reduced 

 in size, and respiration is principally effected by the lining 

 membrane of the gill-chamber, which is thickened, spongy 

 and very vascular, and has its surface increased by being 

 raised into large branching excrescences. A spirit pre- 

 paration in Case 54 shows one side of the gill-chamber of 

 a small female Birgus laid open to display this modification 

 of its lining membrane. 



3rd Tribe, Galatheida, Case 42. — This tribe includes 

 two families — the Porcellanida;, which have a strong 

 general resemblance to the Crabs ; and the Galatheida^, 

 which have rather a resemblance to the Lobsters. The 

 frontal region is prominent, and there are imperfect orbits 

 and imperfect fossae for the lodgment of the antennules. 

 The abdomen is large and symmetrical, and ends in a 

 large caudal fin or swimmeret. The last pair of thoracic 

 legs is small, and is usually carried either alongside of, or 

 benealh, the carai)ace. 



