212 J. G. DE Man : The Fauna of Brackish Ponds. [Vol. II, 



sures 20 mm,, whereas it is 13*3 mm. long without the abdomen. 

 Frontal lobes rounded, little prominent. In the other male, the 

 carapace of which is 38 mm, broad and 25*5 mm. long, the last 

 antero-lateral tooth is hardly larger than the rest and the four frontal 

 lobes are already triangular, the lateral lobes being subacute. In 

 this specimen the anterior margin of the right chelipede carries 

 four spines, that of the left, as usually, three ; in both males 

 there is also but one small spine on the outer side of the wrist. 



2. Tympanomerus stapletoni, sp, nov. 



(Plate xviii, fig, i.) 



Forty-seven males and fifteen females, four of which are egg- 

 bearing. They were collected by Mr. H, E. Stapleton in the Dacca 

 District from a tidal river, the water of which is more or less brackish 

 throughout the year. 



Reg, No, ^^. 

 ^ 10 



As has already been observed by Col, Alcock {Journal Asiatic 

 Soc. Bengal, vol, Ixix, pt, ii, No, 3, 1900, p. 371) the name Tym- 

 panomerus is a most unfortunate one, for, both in Tymp. orientalis 

 (de M.) and in the present species, there are no tympana on the me- 

 ropodites of the ambulatory legs ; it is only in Tymp. pusillus (de 

 Haan), from Japan, that small tympana exist on the meropodites 

 of the last pair of legs. Specimens of Tymp. orientalis and Tymp. 

 pusillus are lying before me, Tymp. stapletoni is intermediate in 

 size between the two other species ; it is somewhat larger than Tymp. 

 orientalis but it does not attain the size of Tymp. pusillus. 

 Both in the male and in the female the distance between the outer 

 orbital angles is one-fifth longer than the length of the carapace, 

 the epistome excluded. From the middle of the cardiac region the 

 upper surface gradually slopes down towards the fronto-orbital 

 margin and towards the moderately deflexed front. As in the two 

 other species, the intestinal region, which is smooth and obliquely 

 deflexed downward, is bounded anteriorly by a transverse ridge that 

 runs between the coxae of the fifth pair of legs ; the intestinal area 

 appears in Tymp. stapletoni higher (longer) in proportion to its 

 breadth than in the two other species. Whereas in Tymp. staple- 

 toni the transverse ridge runs quite parallel with the posterior 

 margin of the carapace, it curves, laterally, a little backward in 

 Tymp. pusillus ; the posterior margin of the carapace measures, 

 in Tymp. stapletoni, two-thirds the distance between the outer orbital 

 angles. The other regions are not or very indistinctly defined. 

 Somewhat nearer to the transverse ridge just described than to a 

 line uniting the outer angles of the orbits, the shallow, transverse, 

 median part of the cervical groove is situated, which median part 

 is interrupted in the middle. The depressed upper surface is 

 marked with transverse, symmetrically arranged, short, impressed 

 lines, which are more numerous on the lateral regions than on the 



