iç)i5-] Fauna of the Chilka Lake : Crustacea Decapoda. 263 



the carpus. The propodus and dactylus are part'ally fused ; taken together, their 

 length is slightly shorter than that of the merus. Close to the apex of the dactylus 

 there is a small tuft of setae. 



The fourth and fifth legs are similar, stouter than those of the third pair. In 

 the fourth pair, which reaches a little beyond the apex of the antennal scale, the 

 merus is the longest segment, almost twice the length of the dacty'us. The carpus 

 is a little more than two thirds the length of the merus and is a little shorter than 

 the propodus and a little longer than the ischium. Except for a few hairs on the 

 latter segment and at the base of the merus the segments are naked. 



There are no longitudinal carinae on any of the abdominal somites and, except 

 for a feeble transverse groove near their posterior margins, the first five abdominal 

 somites are unsculptured ; on the dorsal surface of the third somite, however, not far 

 from the distal margin, is a small tubercle which is a very conspicuous feature in 

 lateral view. The sixth somite is about one and a half times the length of the fifth 

 and is only a trifle shorter than the telson. 



The inner branch of the pleopods is in all cases very short and does not bear an 

 appendix interna. Judging from differences in the proportions of the outer anten- 

 nular flagellum the majority of the specimens obtained are males; in no individual, 

 however, have I been able to find a trace of the appendix masculina (text-fig. 25e). 



The uropods (text-fig. 25/) are a little longer than the telson : the exopod is 

 about three and a half times as long as wide. The telson (text-fig. 25g) is not 

 sulcate above and is much narrowed distally : it has setose margins but no dorso- 

 lateral spinules. The apex (g') is very narrow and is formed by an acutely triangular 

 plate bearing two pairs of fine plumose setae. 1 On either side at the base of this 

 plate is a short and blunt spinule and between these spinules (underneath the plate) 

 are two pairs of very large setae. 



The largest specimen is only about 10 mm. in length ; but is, I believe, fully adult. 



The colouration of the species in life is very variable. As a rule there are two 

 transverse bars of dark reddish-brown pigment, one in the anterior half of the cara- 

 pace and another on the fourth abdominal somite. There are also on the dorsal sur- 

 face several large black or dark brown chromatophores, the distribution of which is 

 very irregular, and frequently a large white spot at the proximal end of the last 

 abdominal somite. The margins of the abdominal pleura are umber brown ; the 

 upper edge of the first legs and the basal segments of the first four legs and last two 

 swimmer ets are dark. 



Pontophilus hendersoni bears little resemblance to any other Indo-pacific species 

 of the genus. Its nearest ally appears to be Pontophilus bispinosus (West wood), a 

 common European species ; from this form, however, it is easily distinguished by the 

 sculpture of the carapace and by numerous minor details. 



The species is described from thirteen specimens found in March 1914, in the 

 outer channel of the Chilka X,ake. They were caught in nets hauled at a depth of 



1 Not shown in text-fig. 25g'. 



