FRYER— FORMATION OF ALDABRA, ETC. 



423 



those he caught but always " mousse," i.e. algse. It was also an undoubted fact that 

 certain beds of algae in the lagoon were always the favourite haunts of hawksbill, which 

 visited them with every high tide. It seems therefore that the evidence is in favour 

 of the hawksbill, like the green turtle, being mainly a vegetarian. 



The remaining turtle found on Aldabra is probably the logger-head (Thalassoehelys 

 caretta). It is scarce, and one was not obtained to make identification certain. The 

 fisherman above mentioned said that this turtle came into the lagoon to eat a small kind 

 of mussel : he had never found algse inside it and did not know where it bred, for it never 

 came up the Aldabra beach to lay its eggs. It appears to be commoner at Cosmoledo 

 than at Aldabra. 



Besides chelonians there are only three other reptiles (two geckoes and one skink) 

 found on Aldabra ; these are 



Hemidactylus gardineri, Boul., 



Phelsuma madagascarensis, var. abbotti, 



Ablephanis boutonii, var. peronii, 



all of which were kindly identified for me by Mr Boulenger. 



Amphibians were not present on the atoll, which is indeed quite unsuited to them. 



(d) Crustacea. All species of land crabs were carefully collected for comparison 

 with those of other coral islands, a comparison which has proved of great interest, as will 

 be seen from the paper by Mr Borrodaile, who was kind enough to take over my collection. 

 The most common form was Cardiosoma, which lives in holes in the rock and appears 

 to act as general scavenger. It was particularly objectionable from its habit of digging 

 holes in the mud which had collected round the wells, which were thus so filled with dirt 

 as to make the water undrinkable. 



Birgus latro, the robber crab, was also very numerous, especially at Takamaka, where 

 it was a great nuisance, for it carried off anything left out at night and also got into the 

 house, unless it was securely closed, and, once inside, occupied itself in pulling everything 

 to pieces in search of food. Eighty were killed on the first three nights, but their 

 numbers did not seem much reduced, though afterwards the camp was left more in peace. 



Their great chelae have immense strength, as is instanced by the fact that a turtle 

 turned on the beach one night had its tail completely hacked off before the morning and 

 was quite dead. 



Two species of land hermit crabs were exceedingly common and showed distinct signs 

 of migration on Esprit Island, a swarm coming down to the sea in December, the females 

 in all cases with eggs. It was most difficult to force the members of this migratory horde 

 to alter their direction : all obstacles were surmounted instead of being avoided. My hut 

 lay directly on the line of migration, but I was quite unable to turn them aside, and 

 during my visit numberless crabs entered and crossed the hut on their way to the sea. 



(e) Inseeta. The insects of the atoll were collected as thoroughly as possible, as it 

 was felt that this group would be large enough to compare both with the insect fauna of 

 other islands and of neighbouring continental lands. The collections have been distributed 

 to specialists on the various orders, whose papers will speak for themselves. It may be 



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