igiS-] Fauna of the Chilka Lake : Crustacea Decapoda. 221 



is either fresh or salt. It does not, however, extend so far up the channel as the 

 allied species and it has not been found south of Manikpatna. It is common on the 

 adjacent shores of the Bay of Bengal. 



The breadth of the carapace in the largest specimen, a male, is 53 mm. 



0. platytaysis is known from both coasts of Peninsular India and from Ceylon. 



Genus GELASIMUS, LatreiUe. 

 1897. Uca (Luach, not of Latreille), Rathbuii, Proc. Biol. Soc. Wasliington, XI, p. 154. 

 1900 Gdasimits, Alcock, Joitni. Asiaf. Soc. Bengal, LXIX, p. 350. 



Gelasimus annulipes, Latreille (M.-Edw.) 



1900. Gdasiinus unniilipes, Alcock, Journ. Asiat Soc. Bengal, LXIX, p. 353. 



The numerous specimens agree well with other examples in the Indian Museum 

 determined by Alcock; the form of the hand in the adult male corresponds very 

 closely with the figure given by Milne-Edwards.' The examples are, however, very 

 much smaller than those found in other parts of India, for the breadth of the cara- 

 pace in the largest male does not exceed 125 mm. 



Nobili ' has drawn attention to a difference in the form of the chela in specimens 

 from the eastern and western portions of the Indo-pacific region. To the eastern 

 form he gave the name var. ovientalis, but subsequently notes* that that form is 

 identical with G. perplexus, M.-Edw.*, a name relegated by Hilgendorf and Alcock 

 to the synonymy of G. annulipes. Still later. Miss Rathbun ' recognized G. perplexus 

 as a distinct species and gave photographic illustrations of it. The specimens she 

 examined were found at Ceram I. and at Makassar in Celebes, many specimens of 

 typical G. annulipes being also found at the latter locality. From the last of these 

 records it is evident that the two forms are not, as Nobili supposed, restricted to 

 separate parts of the Indo-pacific region. But, until further evidence is available, 

 the status of G. perplexus must remain doubtful. So far as one is able to judge — 

 for Miss Rathbun gives no description — it is only in the toothing of the large claw of 

 the male that the differential characters are to be found, and in this respect the 

 species of Gelasimus often show a wide range of variation. It is only by the exam- 

 ination of long series of specimens from different localities that the point can be 

 determined in a satisfactory manner. 



A colony of Gelasimus annulipes was found to have established itself in March 

 1914, on one of the islands in the outer channel of the lake close to Manikpatna. The 

 specimens were living on a narrow strip of land between the water's edge and the 

 coarse grass with which tlie island was covered. We noticed that the larger indivi- 

 duals occupied the (apparently) more eligible situations close to the water line, while 



' Milne-Edwards, .4mm. Sci. nat. Zool. (3), XVIII, pi. iv, fig. 15& (1S52). 



^ Nobili, Boll. Mils. Torino, XVI. No. 397, p. 13, text-figs. A, B (1901). 



8 Nobili, Ann. Sci. nai. Zool. (g), IV, p. 312 {1906). 



^ Milne-Edwards, Ann. Sci. nat. Zool. (3), XVIII, p. 150, pi. iv, figs. 18, iSk (1852). 



^ Rathbun, Bull. Mus. Coinp. Zool,, Harvard, LII, p. 306, pi. i, figs, i, 2 (1910). 



