OCYPODIDAE. 



To this family belong some well known and widespread tropical genera of Crabs, that 

 are mostly characterized by their slender, often greatly elongate eye-stalks, and the narrow 

 front, and in some cases by the enormous development of one of the chelipeds in the cf. All 

 the species keep strictly to the shore and live on sandy and muddy beaches, between flood- 

 and ebbline-, the majority has burrowing habits, each individual boasting of a separate hole 

 to itself, to which it rapidly retreats when danger is approaching. Such genera as Ocypoda 

 and Uca (= Gelasimus), that live in countless numbers in suitable localities, do not fail to 

 attract the attention of even the layman. There is in this family a clearly-pronounced tendency 

 to estuaries, mangrove-swamps and even to fresh water, though no species may be called 

 strictly fluviatile. 



Recent writers have distinguished three subfamilies : Ocypodinac, Mictyrinac and Macroph- 

 thalminae, that are well defined by Alcock l ) and Borradaile s ). 



Subfam. Ocvpodinae. 



The subfamily comprises the best known and most conspicuous representants of the family, 

 viz. the genera Ocypoda and Uca, and, besides, only the genus Heloecius 8 ). 



i. Abdomen of cf almost as broad at base as the sternum ; chelipeds subequal. 



Epibranchial regions much inrlated Heloecius 



Abdomen of cf much narrower at base than the sternum ; chelipeds always 



unequal 2 



2. Corneae of eyes very much bulging, occupying nearly the whole ventral part 



of the eye-stalks ; the latter club-shaped. Chelipeds of cf not very unequal Ocypoda 

 Corneae of eyes small, at end of eye-stalks ; the latter slender and thin. 



Chelipeds of cf very unlike, one being enormously developed Uca 



1) Journ. As. Soc. Bengal, v. 69, 1900, prt 2, p. 342 — 343. 



2) Ann. Mag. Nat. Hist. (7) v. 19, 1907,, p. 485 -486. 



3) The genus Acanthoplax of H. Milne-Edwards, with only one species (inhabiting the coast of Chile) is now fused into Uca, 



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