1915J Fauna of the Chilka Lake : Crustacea Decapoda. 289 



segment of the mandibular palp is not widened distally, the exopod of the outer 

 maxillipedes is much shorter, the three distal subsegments of the carpus of the second 

 legs are of equal length and the telson is narrower, with the apex evenly rounded. 



Living specimens of 0. striaticauda were for the most part transparent, the 

 greenish visceral and hepatic masses being clearly visible through the walls of the 

 carapace. The eyestalks, antennules and antennae were pale red and the oral 

 appendages, maxillipedes and first two pairs of legs bright red. On the first abdomi- 

 nal somite there were two transverse rows of red pigment spots and one similar 

 row on each of the succeeding somites. The pleural margins were also red and the 

 eggs borne by the ovigerous female were bright green. 



0. striaticauda is apparently very scarce in the Chilka Lake : in all, only eight 

 specimens were obtained. They were found in the outer channel in March, when 

 the water was as salt as that of the sea outside the lake area, and in September, 

 when it was entirely fresh. Three individuals were caught on the clean sandy 

 bottom between Manikpatna and the mouth of the lake in company with Pontophilus 

 hendersoni, while the remaindei were obtained on the muddy ground in the vicinity 

 of Barhampur I. No specimens were met with in the main area of the lake. The 

 ovigerous female was found in March in salt water. 



In addition to the Chilka lake specimens, there are in the Indian Museum 

 numerous other examples obtained by Mr. F. H. Gravely in September 1914, in the 

 Cochin backwaters near Ernakulam. There are ovigerous females among these speci- 

 mens, though none were found at the same time of the year in the Chilka Lake. 

 A few specimens were also taken in the Ennur backwater in January 1915, by Dr. 

 Annandale. They were living on a bottom of almost pure sand in water of very low 

 specific gravity. One female bore eggs. 



Genus ATHANAS, Leach. 



1899. Athanas, Coutière, Ann. Sei. nat., Zool. (8), IX, p. 323. 



Among the species of this genus most marked differences exist in the degree of 

 development of the first pair of legs. In most forms those of the male are greatly 

 enlarged, much as in the genus Alpheus, and may be symmetrical or asymmetrical. 

 In females the first legs may resemble those of the male, or one or both limbs may 

 be small and slender. 



In the species of Athanas found in the Chilka Lake the first pair of legs presents 

 features of unusual interest and it seems desirable therefore, in the first place, to 

 summarise our knowledge of the development of these limbs in the various forms 

 that have been described. 1 



neous, for Ortmann has apparently failed to discern the true division between the merus and ischium 

 and has represented what is really the produced lower distal angle of the latter as a spine at the base 

 of the former. 



1 A most valuable key to the species of Athanas has been supplied by de Man, Decap. ' Siboga' 

 Exped., II, Alphddae, p. 146 (1911). 



