Crustacea Decapoda and Stomatopoda. 241 



Though the two forms are clearly allied there are many conspicuous differences 

 between these young individuals and S. foxi. The carapace is decidedly broader than 

 long and its lateral margins are posteriorly divergent. The orbital tooth is narrower, 

 the first epibranchial tooth more prominent and a strong ridge runs obliquely inwards 

 and backwards from the rudimentary second epibranchial tooth. The walking legs 

 are much stouter, the merus of the penultimate pair being scarcely more than two 

 and a half times as long as broad. 



It is possible that these are young examples of the form described by lyanchester 

 from "lyacom" and Bukit Besar as Sesarma maculata, de Man, but they differ notice- 

 ably from de Man's description, especially in the form of the penultimate segment of 

 the male abdomen. It appears to me exceedingly improbable that the true 5. macu- 

 lata, which was described from Flores, can occur in the Malay Peninsula. 



Sesarma politum, de Man. 



1888. Sesarma polita, de Man, Joitrn. Linn. Soc, XX, p. 189, pi. xiii, figs. 7-9. 

 Three specimens were found at the mouth of the Tale Sap on the shores of Kaw 

 Deng. The largest is a female with carapace 21 '5 mm. in length. In the smallest 

 the carapace is only 7*5 mm. long and the second epibranchial tooth is undeveloped. 



Genus Hclice, de Haan. 

 Helice tridens^ de Haan. 



1894. Helice tridens, Ortmann, Zool. Jahrb. Syst., VII, p. 727. 

 A single male, with carapace 26 mm. in breadth, was presented to Dr. Annandale 

 by Prof. S. Yoshida. It was obtained in brackish water near Osaka in Japan. 



Genus Clistocoeloma, A. Milne-Edwards. 

 Clistocoeloma merguiense, de Man. 



1900. Clistocoeloma merguiense, Alcock, Journ. Asiat. Soc. Bengal, 'L,X.IK, p. 429. 

 Two specimens, a male and a female, were obtained by Dr. Annandale in fresh 

 water near the mouth of the Patani River in the Siamese Malay States. The cara- 

 pace of the male is 8-3 mm. in length and 9-4 mm. in breadth ; that of the female is 

 9-9 mm. in length and ii-8 mm. in breadth. The specimens were found in burrows in 

 wet mud, under the trunk of a dead palm tree. 



Family POTAMONIDAB. 

 In determining the ten species of river-crabs in the present collection I have 

 followed the classification proposed by Alcock in 1910.' Alcock divides the family 

 into two groups^ the Potamoninae and the Gecarcinucinae, mainly on characters 

 drawn from the structure of the mandibular palp. In the former subfamily the ter- 

 minal segment of the palp is " simple, sometimes thickened at the base for the attach- 

 ment of a bunch of hairs," whereas in the latter it is " cut into two lobes which em- 



1 Alcock, Cat. Indian Decap. Crust., I, fasc. ii, p. 17 (1910). 



