CRUSTACEA OF THE MERGUI ARCHIPELAGO. 185 
millim. 
Distance between the extraorbital teeth ........ 112 
iemevh of the cephalothorax .................- 93 
Eecadumon the fronts Vo... Puts. ob oe Satie ess = 
102. SesarmMa Epwarpst, 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. Forty 
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 astream. Four of the individuals found 
in water were infested with Sacculine. Four 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 Hdwardsi is therefore 
closely allied to Sesarma intermedia, de Haan, and to S. 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 8. éntermedia and S. 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 
teeth 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 11:63, but this is an individual variation. The upper surface 
is as little convex as that of 8. senensis, and presents quite the 
