1900.] A. Alcock — Carcinulogical Fauna of India. 345 



dispute, and I have published my own observations on that of 0. macrocera in the 

 Administration Report of the Marine Survey of India for the year 1891-92 (re- 

 printed in the Annals and Magazine of Natural History for 1892). Dr. A. R. Anderson 

 has published a note on the sound prodnced by 0. ceratophthalma in this Journal for 

 the year 1894. 



My own opinion is that these crabs use the stridulating-organ when in their 

 burrows — which undoubtedly are private property— to warn intending intruders of 

 the herd that the burrow is occupied, and thus to prevent the burrow becoming 

 crowded to suffocation-point. This, of course, need not be its exclusive use. 



Key to the Indian species of Ocypoda. 

 I. No stridulating ridge on the inner surface of .the palm : 

 eyestalks not prolonged beyond the eyes in the form of a 



style 0, cordimana. 



II. A stridulating ridge on the inner surface of the palm : 

 eyestalks (except sometimes in the young) prolonged 

 beyond the eyes to form a horn or style : — 



1. Length of the stridulating organ much more than 

 half the greatest breadth of the palm : antero- 

 lateral angles of the carapace well pronounced : — 



i. Fingers of both chelipeds pointed : — 



a. Stridulating ridge narrow, consisting entirely 

 of small tnbercles : no brushes of hairs on 



the propodites of any of the legs 0. platytarsis . 



b. The stridulating ridge consists of tubercles 

 gradually passing into striae : the anterior 

 surface of the propodites of the first two 



pairs of legs thickly furnished with hairs ... 0. ceratophthalma. 

 ii. Fingers of the smaller cheliped expanded at tip : 



the stridulating ridge consists entirely of striae... 0. macrocera. 



2. Length of the stridulating organ much less than 

 half the greatest breadth of the palm : antero- 

 lateral angles of the carapace rounded off ,. 0. rotundata. 



The synonomy of the species of Ocypoda has been discussed, at 

 length, by Ortmann (Zool. Jahrb., Syst., X. J897-98, p. 359), who has 

 had access to a great deal more material than I have. It would be in- 

 advisable, therefore, for me, working on a collection made almost entirely 

 in India, to attempt any independent criticism of the older work ; so 

 that, in dealing with the Indian species, I shall generally restrict my 

 citations to the papers of Ortmann and the other authors (Kingsley and 

 Miers) who have made a revision of the genus. 



43. Ocypoda ceratophthalma (Pallas), Ortm. 



Cancer ceratophthalmus, Pallas, Spicilegia Zool. IX. p. S3, pi. v. figs. 7, 8. 

 Cancer cursor, Herbst, Krabben, I. ii. 74, pi. i. figs. 8, 9. 



Ocypoda ceratophthalma, Fabricius, Ent. Syst. Suppl. p. 347: Milne Edwards 

 Hist, Nat, Cruet, II. 48, and Cuvier Regne An, Crust, pi. 17; Kirjgsley, Proc. Ac. 



