238 ZOOLOGY OF THE FAR EAST. 



S. siamense was described by Miss Rathbun from the eastern side of the Gulf of 

 Siam, from Koh Kong, Koh Kut and Koh Chick. 



Scsarma foxi, sp. nov. 

 I take this opportunity of describing a very interesting species of Sesarma ob- 

 tained in 1914 by Mr. B. H. Buxton at a height of 2000 ft. on Gunong Raya, in Langkawi 

 I., N. of Penang. Species of this typically estuarine genus have seldom been recorded 

 from considerable altitudes, though a number have been taken on land some distance 

 from the coast-line. The following list, so far as I am aware, comprises all species of 

 the gentis that have been recorded from definite heights above sea-level. 

 Sesarma maculata, de Man. Halmahera, 2000 ft. 

 "Sesarma maculata," Lanchester ( ? de Man). Bukit Besar, near Patani, 



Siamese Malay States, 2500 and 3500 ft. 

 Sesarma trapezoidea, Guérin. Halmahera, 2500 ft. 

 Sesarma thelxinoe, de Man. Andamans, 800 ft. 

 Sesarma sp. (vide infra, p. 240). Penang, 1200 ft. 



Fig. 3. — Sesarma foxi, sp. nov. 



It appears probable that in these places the Sesarma have been able to adopt a 

 strictly terrestrial mode of life and to ascend to considerable altitudes owing to the 

 damp climate that prevails ; in the Andamans the entire absence of competitors in 

 the form of Potamonidae is doubtless an important factor. 



The carapace in S. foxi is exactly quadrilateral, its length being precisely, or al- 

 most precisely, equal to its breadth ; the lateral margins are strictly parallel, the 

 breadth at the base of the third pair of legs being equal to that at the outer orbital angle. 

 The carapace is shghtly convex fore and aft and from side to side and is everywhere 

 distinctly rugose and faintly pitted. A trifoliate gastric areola is distinct and behind it 

 there is a slight prominence on the cardiac region ; these areas are a little smoother 



