286 ZOOLOGY OF THE FAR EAST. 



rostrum, posterior and lower margins of each abdominal somite, the margins of the 

 telson and a longitudinal streak on each branchial region dark olive green. Suffusions 

 of the same colour were sometimes present on other parts of the body. The eggs 

 were greenish. 



The numerous specimens in the collection were all obtained in the lower reaches 

 of the Patalung River and in the Tale Sap in Lower Siam. In the inner lake 

 they were common in fresh water, among weeds at the mouth of the Patalung River 

 and at the edges of the lake in the same neighbourhood. In the outer lake they 

 were equally abundant, living among weeds round the island of Koh Yaw in water of 

 specific gravity i-oo6. 



Ovigerous females were obtained in both parts of the lake, but the size of the 

 eggs— 0'65 to 070 mm. in length and 0-40 to 0-45 mm. in breadth — -does not differ in 

 correlation with the different specific gravity of the water. It will be noticed that the 

 eggs of specimens obtained in slightly brackish water are nearly twice the size of those 

 of C. gracilirostris living in similar situations. This fact, more than any other, has in- 

 duced me to retain C. gmcillima as a distinct species. 



Lanchester was in some little doubt as to the precise locality at which his speci- 

 mens were obtained. They were found by Dr. Annandale and Dr. R. Evans in 1899, 

 when attached to the ^'Skeat" Expedition, and were caught in the inner lake of 

 the Tale Sap, just inside the mouth of the Patalung River. The species has not been 

 recorded from any other locality. 



Caridina denticulata (de Haan). 



1849. Caridina denticulata, de Haan, in Siebold's Fauna Japonica, Crust., p. 186, pi. xlv, 



fig. 8 {as Hipfolyte). 

 1894. Caridina denticulata, Ortmann, Proc. Acad. Sci. Philadelphia, p. 406. 

 1902. Caridina denticulata, Rathbun, Proc. U.S. Nat. Mus., XXVI, p. 49. 

 1902. Caridina denticulata, Doflein, Abandl. math.-phys. Klasse Bayer. Akad. Wiss. Miinchen, ^ 



XXI, p. 632, text-figs. 

 1905. Caridina denticulata. Bouvier, Bull. sci. France Belgique, XXXIX, p. 74. 

 1914. Caridina denticulata, Balss, Abhandl. math.-phys. Klasse Bayer. Akad. Wiss. Milnchen, 



Suppl. Bd. II, Abh. 10, p. 24, 



This species has been recorded both from China and Japan and good series from 

 each of these countries are in Dr. Annandale' s collection. On comparison certain 

 small but apparently constant differences are to be found between the two sets 

 of specimens and I have, in consequence, given the Chinese form subspecific rank. 



An important character of C. denticulata is the presence of an acute for- 

 wardly directed tooth on either side of the carapace at the antero-inferior angle. 

 Though clearly shown in Doflein' s figures, and less distinctly in that of de Haan, 

 its existence is not mentioned in any of the published descriptions. The antero- 

 inferior angle of the carapace ' is rounded off in most known species of Atyidae, but 



1 Bouvier in his key to certain species of Caridina 41913) separates some forms by the presence or absence of spines 

 at the points he calls " l'angle orbitaire " and " l'angle sous-antennaire." By the former term he apparently refers to 

 the angle on the anterior border of the carapace which is frequently called the autennal angle or antenual spine and by 



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