XII. NOTES ON DECAPOD A IN THE 

 INDIAN MUSEUM. 



IV. — Observations on the primitive Atyidae with 

 SPECiAi. reference to THE GENUS Xiphocafidina. 



By Stanley Kemp, B.A., Assistant Superintendent ^ Indian 



Museum. 



For the last few years efforts have been made to improve 

 the collection of Atyidae in the Indian Museum and, thanks 

 to the energy displayed by numerous correspondents, the series 

 will, it is hoped, shortly become thoroughly representative of this 

 important part of the Indian freshwater fauna. In course of time 

 a full report on this famil}^ and on the Palaemonidae will be 

 issued, forming a part of the Museum Catalogue of Indian Deca- 

 pod Crustacea. 



The At5dd fauna of the Indian Empire comprise-s, so far as is 

 at present known, only three genera, Atya, Caridina and Xiphoca- 

 ridina. Ortmannia (Atyoida) does not seem to occur, and this, in 

 view of Bouvier's theory of the mutational origin of that genus 

 and of Atya, is a most unfortunate circumstance. It is, however, 

 still hoped that specimens will be found which will provide 

 material for some further consideration of this interesting question. 



Atya appears to be very scarce. A few specimens from the 

 Andamans are the only Indian representatives of the genus in the 

 collection, while in addition there is a single example from Ceylon. 

 Caridina, the prevalent genus, occurs in great abundance in ever}' 

 suitable locality, inhabiting both fresh and brackish water and 

 ascending to altitudes of at least 6,000 ft. Of Xiphocaridina a single 

 species onl}' is known, obtained at Tezpur, on the north bank of 

 the Brahmaputra R. in Assam, and in the native state of Manipur 

 further to the east. It is with this last form that the present 

 note is concerned. 



The Atyidae as a whole must be regarded as a very primitive 

 family of Caridea, in spite of the fact that the peculiarly modified 

 chelae indicate a considerafjle degree of specialization. Xiphocari- 

 dina is one of the most primitive of the known genera, and it is 

 through such forms as this and Xiphocaris that the common 

 ancestry of the Atyidae and the deep-sea pelagic shrimps of the 

 family Hoplophoridae has been traced. Bouvier (igoqrt), follow- 

 ing Ortmann (1895), has laid great stress on this interesting feature 

 of Caridean evolution, and his careful researches leave no room 

 for doubt on the point. 



