CRUSTACEA OF THE MERGUI ARCHIPELAGO. 171 



The anterior legs are also nearly alike in both species, but 

 the prominences of the upper margin of the mobile finger have 

 a characteristic form distinctive in each. In the male of S. aspera, 

 the upper margin of the mobile finger presents a row of 16 or 17 

 transverse oval tubercles, each of which is symmetrical with regard 

 to a median, transverse, smooth ridge, the tubercles resembling a 

 Chiton^ as iu S. hidens, de Haan. In 8. Melissa the upper margin 

 of the mobile finger presents a row of 14-15 prominences, which 

 are also transverse, but are not symmetrical and do not resemble 

 a Chiton. The anterior (distal) declivity of each tubercle is 

 larger than the posterior (proximal) declivity, and the former 

 is distinctly excavated, the prominences being somewhat horse- 

 shoe-shaped. In other particulars, the hands are perfectly similar 

 in the two species ; and in each the anterior margin of the arm 

 presents an acute spine, and its upper margin terminates also in 

 a small acute tooth. 



The meropodites have the same form, being equally enlarged 

 in both species. The carpopodites and propodites are, however, a 

 little more slender in ^S*. Melissa than in 8. aspera, and the dactylo- 

 podites are a little shorter in proportion to the length of the 

 propodites. 



The upper surface of the cephalothorax is ornamented with 



violet markings, and the propodites of the ambulatory legs with 



two violet rings, parallel to one another. 



Dimensions : — 



millim. 

 Distance between the external orbital angles .... 15 



Length of the cephalothorax , ...... 12| 



Breadth of the front 8| 



Sesarma Melissa stands in the same relation to Sesarma aspera 

 as Sesarma Saswelli to Sesarma hidens. 



94. Sesarma picta, de Saan. 



Grapsus (Pachysoma) pictus, de Haan, Fauna Japon. Crust, p. 61, 

 Taf, xvi. fig. 6. 



Sesarma picta, Milne-Edwards, Ann. Sci. Nat. 3° serie, t. xx. p, 184 ; 

 de Man, Notes from the Leyden Museum, vol. ii. p. 22. 



The collection contains one young female specimen, found in 

 fresh water on Sullivan Island. 



The distance between the external orbital angles measures 

 12| millim., the front between the eyes 63 millim., and the 

 cephalothorax is 10 millim. long. 



