226 Memoirs of the Indian Museum. [Voi,. V, 



to the mouth of the burrow there is always a well-constructed avenue or ff run/' two 

 to four inches in length, formed by smoothing the sand and heaping it up on either 

 side. The pellets brought up from the burrow are cast to one side of this fc run" 

 and, as a rule, form a triangular patch visible on the smooth surface at a consider- 

 able distance. The crabs seem never to wander beyond the limits of the " run." 



D. pertinax occurs commonly on the sandy bars and islands in the outer channel 

 and is abundant, both when the water is fresh and when it is salt; it does not in 

 our experience live within a mile of the actual mouth of the lake. The latter region, 

 during the salt-water season in March 19 14, was inhabited by a colony of D. clepsy- 

 drodactylus. The ovigerous females, of which only two were found, were obtained in 

 March. They accompanied other individuals on the shore. 



The type specimens are registered under no. 8937/10. 



Dotilla clepsydrodactylus, Alcock. 



1900. Dotilla clebsydrodactylus, Alcock, Journ. Asiat. Soc. Bengal, LXIX, p. 367 ; and Illust. Zool. 

 'Investigator ' , Crust., pi. lxiii, figs. 2, 2a (1902). 



The specimens agree perfectly with the types of the species and with Alcock's 

 account and figures except that the tooth in the middle of the fixed finger is in no case 

 so well developed as is indicated in the original description. Even in individuals in 

 which the carapace is 6 mm. broad, i.e. of a size practically identical with that of the 

 largest type specimen, the tooth has merely the form of a low serrated ridge and is 

 only a trifle more prominent than in the preceding species. 



In addition to the points mentioned by Alcock it may be noted that the eye is 

 a little flattened and in dorsal view appears almost bilobed, and that there are three 

 finely serrated carinae on the lower surface of the chela, terminating on the fixed 

 finger. Two of these carinae run parallel to one another on the outer aspect of the 

 inferior surface, while the third, situated on the infero-internal border, diverges from 

 them proximally : the lower surface of the palm is in consequence sharply defined, 

 flat and triangular in shape. By the use of this character, coupled with that of the 

 areolation of the carapace (very exactly shown in Alcock's figure) it was easy to dis- 

 tinguish even the smallest specimens of this species from those of D. pertinax. 



It may ultimately be shown that D. clepsydrodactylus is synonymous with D. 

 intermedia , de Man, from Sullivan I. in the Mergui Archipelago. I have examined 

 some of the original specimens of the last named species, all of them, unfortunately, 

 small and in rather poor condition. The resemblance to immature D. clepsydrodacty- 

 lus is extremely close, but in the absence of adults from the Mergui Archipelago 

 it is impossible to arrive at any satisfactory conclusion. 



Fresh examples of this species were easily distinguished from D. pertinax by the 

 absence of the dark speckling on the sub-hepatic and pterygostomian regions. 



In March 1914, a colony of D. clepsydrodactylus was found to have established 

 itself just inside the mouth of the lake and a stray individual was obtained at the 

 same time in company with D. pertinax on the sand-bar opposite Manikpatna. At 



