CEirSTACEA OF THE MERGUI AECHIPELAGO. 185 



millim. 



Distance between tlie extraorbital teeth 11| 



Length of the cephalothorax 9| 



Breadth of the front 6| 



102. Sesakma Edwardsi, n. sp. (PI. XIII. figs. 1-4.) 



I have much pleasure in dedicating this new species to Prof. 

 A. Milne-Edwards, by whose kindness I have been enabled to 

 study many typical specimens of this difficult genus preserved in 

 the Paris Museum. 



The collection contains 58 specimens of this species. Eorty 

 specimens were collected on Sullivan Island, and of these 29 were 

 obtained in fresh and brackish water, and eleven from underneath 

 stones on a hillside above a stream. Pour of the individuals found 

 in water were infested with SacculincB. Pour specimens were 

 obtained in Elphinstone Island. The labels which accompanied 

 the twelve remaining specimens have been lost. 



This species, together with its variety crassimana, belongs to 

 the division of this section of the genus in which the distance 

 between the extraorbital teeth is greater than the length of 

 the cephalothorax, and in which the cephalothorax is scarcely 

 convex longitudinally, and has its lateral margins completely 

 parallel. The upper margin of the arms of the anterior legs 

 does not terminate in an acute tooth, and the anterior margin 

 is never armed with a spine, Sesarma Edwardsi is therefore 

 closely allied to Sesarma intermedia, de Haan, and to 8. sinensis, 

 M.-Edw. ; it may, however, be distinguished by the form of the 

 male abdomen, which is much more enlarged, and by the struc- 

 ture of the anterior legs, the carpopodite being armed, at the 

 internal angle of the upper surface, with a short, acute, depressed 

 tooth, which is not found in S. intermedia and 8. sinensis, and 

 by the inner surface of the palm never presenting a transverse 

 granulated ridge. 



The cephalothorax completely resembles that of ;S^. sinensis, 

 in the proportion of the distance between the extraorbital 

 teetli to the length of the cephalothorax, and in the propor- 

 tion of the distance between the extraorbital teeth to the 

 breadth of the front, the former being as 9 : 8, and the latter 

 as 11 : 6, in both species. Sometimes the latter proportion is 

 as 11 : Q\, but this is an individual variation. The upper surface 

 is as little convex as that of 8. sinensis, and presents quite the 



