I9I5-1 



Fauna of tlic Cliilka Lake : Crustacea Decapoda. 



271 



a slight decrease in the relative length of the ischium is counterbalanced bj' an 

 increase in the lengths of the palm and dactylus. 



In life, females and young males differ noticeably in colour from adults of the 

 latter sex. In young specimens and in females there is a pair of dark dorso-lateral 

 streaks on the carapace and distinctive dark lateral markings. The first of these is 

 situated on the gill-cover and is U-shaped with the anterior limb of the \J turned for- 

 wards towards the base of the antennal scale. Behind this is another mark which is 

 P-shaped and placed, not on the branchiostegite, but on the inner wall behind the 

 gills. On the abdomen there is a faintly marked transverse patch at the end of 

 the third abdominal somite and the margins of the pleura are dusky. The antennules 

 are dull red and there is a conspicuous streak of reddish chromatophores up the 

 middle of the antennal scale All the legs are suffused with reddish-purple, the joints 

 being tinged with orange yellow. The chelae of the second legs are not marbled as in 

 the young individuals referred to P. malcohnsoni , and the fingers are reddish or 

 colourless. The telson and uropods are stained with reddish-brown. In very large 

 females the margins of the abdominal pleura are whitish and the claws of the second 

 legs obscurely marbled with yellow. The distinctive colour markings on the carapace 

 are faint or absent and there is, in general, a very marked resemblance to adult 

 females of P. malcohnsoni. 



Large males are of an almost uniform dull bluish or greenish-grey colour which 

 becomes darker and has a mottled appearance on the telson and uropods. The 

 antennules and antennae are grey and the scale is transparent in its external half, 

 but possesses internally a broad dark grey longitudinal band. The second legs are 

 dark bluish-grey, paler beneath and conspicuously mottled above with a very pale 



