72 A Guide to the Zoological Collections in the 



two are very common in the jungles of the Anda- 

 man Islands. 

 2nd Family, OcypodJdae — Largely shore and estuarine 

 crabs burrowing in the sand and mud ; a few 

 species inhabit deep water. The Indian genera 

 shown are Ocypoda, Gelasivius and Macroph- 

 thahniis. 

 The Ocypoda live together in " warrens " on the sea- 

 shore of tropical countries, and derive their name from their 

 wonderful swiftness of foot. Some species possess stridu- 

 lating organs. Gelasinius also lives in "warrens" among 

 the mud flats of tidal creeks and estuaries. The males of 

 Gelasimus have one of their chelae not only enormously 

 magnified, for the purpose of fighting in the periodic con- 

 tests that occur for the possession of the females, but also 

 beautifully coloured, apparently for the purpose of attract- 

 ive display before the females. Observe the dried speci- 

 mens of Gelasimus annulipes, Edw., in Case 51 in which 

 this wonderful, difference between the male and the fe- 

 male is contrasted. 



3rd Family, Grapsjdse — largely rock and reef-haunting 



crabs. The genera Grapsus, Goniograpsus, 



Cyclograpsus, Varuna, Sesarma, Metasesarma, 



Plagusia, all from the Indian Seas, represent 



this family in the Gallery. Most of the Grap- 



sidae are extremely bold, active and alert. 



4th Family, Pinnotherldas — Small and often soft-shelled 



crabs, many of which are commensal with 



Mollusks and Echinoderms. The genera Xan- 



thasia and Hymenicus, both found in the Indian 



Seas, illustrate this family. 



3rd Tribe, Oxyrhyncha, Case 64. — This tribe, as its name 



of Oxyrhynch or '"Sharp-nose" implies, is characterised 



by having the carapace prolonged in front into a sharp 



spine somewhat like the " rostrum " of a prawn. Very 



many of the Oxyrhynchs have a globular and relatively 



small carapace, together with long slender legs, and hence 



