I9I5-] 



Fauna of the Chilka Lake : Crustacea Decapoda. 



215 



granules on either side of the carapace are differently disposed (they form a A-shaped 

 figure in P. olivacea) and there are distinct angulations at the points when these rows 

 meet the postero-lateral borders; (iv) the posterior margin is bilobate in the adult 

 male (trilobate in P. olivacea); (v) there are two pairs of large tubercles on the 

 sternum of the adult male and the margin bordering the anterior part of the abdomi- 

 nal cavity is not granulate ; (vi) the palm of the chelae is proportionately more 

 slender and is as long as the fingers ; (vii) in the abdomen of the male the penulti- 

 mate piece is broadest distally, and is at this point sharply angulate on either side. 



It also bears some resemblance to P. sexangula, Alcock ', recorded from the 

 Godavari coast and the Persian Gulf and also obtained a few years ago by Dr. 

 J. T. Jenkins in the Matlah river in the Gangetic delta. P. alcocki differs, however, 

 from this species in many notable points, (i) in the narrower front and general shape 

 of the carapace, (ii) in the presence of a n-shaped pattern of tubercles on either side 

 of the carapace in place of a single oblique ridge, (iii) in the much shorter chelipedes 

 and in the absence of a granular ridge on the upper surface of the palm, and (iv) in 

 the abdomen of the male, which is composed of three instead of two pieces. 



From P. fuliginosa, Targioni Tozzetti" 2 , P. alcocki is more obviously distinct, 

 differing in its much broader form., in the different arrangement of the granules on the 

 carapace, in the proportions of the chela and in the shape of the abdomen of the male. 



In life the colour of the carapace was very pale french grey, with fine speckles 

 of dull purplish-red, aggregated to form irregular sinuous markings. The ventral 

 surface was whitish and the legs a very pale brown. 



When caught, specimens adopt a catalyptic attitude, folding their legs and hold- 

 ing them with the ischial and meral segments directed vertically downwards from 

 the carapace (text-figs. 3a, b). The Ebalia, on the other hand, though they kept 

 quite still and also appeared to be 

 simulating death, held their legs 

 normally, with the meral segments 

 tucked up against the carapace. 



Philyra alcocki was sometimes 

 found in company with Ebalia 

 malefactrix, but appeared to be 

 much less common. It is repre- 

 sented in the collection by sixteen 

 specimens obtained over an area 

 ranging from Rambha in the south 

 to Barkul and Nalbano in the 

 north on a bottom of mud or 



muddy sand and at depths of from 5 to 10 ft. In September it occurred rarely in 

 the outer channel in fresh water. 



1 Alcock, Journ. Asiat. Soc. Bengal, LXV, p. 241, pi. vii, fig. 2 (1896). 



% Targioni Tozzetti, Zool. Viag. R. P. 'Magenta ' , Crost., p. 201, pi. xii, figs. 3, a-g (Florence, 1877). 



cu. 



b. 



Fig. 3. — Philyra alcocki, sp. nov. 



A female sketched from life in the attitude which the species 

 adopts when irritated. 



a. Dorsal view. b. Ventral view. 



