XVII. NOTES ON CRUSTACEA DECAPODA 

 IN THE INDIAN MUSEUM. 



XIV. On the occurrence of the Caridean genus Disci as 

 IN Indian Waters. 



By StanIvEy Kemp, Sc.D., Superintendent, Zoological Survey 



of India. 



(Plate VIII). 



Among a collection of Decapod Crustacea which I made 

 during a short visit to Port Blair in the Andaman Is. in the 

 spring of 1915, there occur five specimens of a small prawn of 

 rather unusual interest. The marine fauna of Port Blair proved 

 so extremely rich that, in the time at my disposal, it was not 

 possible to examine all the forms obtamed with any degree 

 of thoroughness and the remarkable nature of the specimens 

 was thus not noticed at the time of their capture. 



The specimens prove to belong to the little known genus 

 Discias, described by Miss Rathbun in igo2 from three specimens 

 obtained by the Hopkins Stanford Galapagos Expedition at Alber- 

 marle Id. in the Galapagos group. Discias shows little affinity with 

 any other genus of Caridea and Miss Rathbun referred it to a new 

 family, the Discidae, which hitherto has been known only from 

 her original description. It is not a little remarkable that the 

 genus should reappear in Indian waters, for the Andamans are 

 separated from the Galapagos Is. by almost exactly half the circum- 

 ference of the globe. 



In the family Discidae, or, as I would prefer to call it, the 

 Disciadidae, we find characters which appear to be primitive 

 combined with others which indicate a high degree of specializa- 

 tion. The persistence of exopods on all five pairs of legs would 

 seem to be a very primitive feature and the second maxillipeds are 

 also less highly organized than in most Caridea. On the other 

 hand the mandibles and maxillae are not primitive and the 

 legs of the first pair, in the extreme reduction of the carpus and 

 in the remarkable structure of the fingers, present characters 

 which are without parallel in the Macrura and afford clear evi- 

 dence of specialization. 



Miss Rathbun considers that the family is related to the 

 Atyidae and Hoplophoridae but, except for the exopods on the 

 legs, I can find little to recommend this view. The molar and in- 

 cisor processes of the mandible are separated in Discias by a 

 deep cleft and the proximal endite of the maxilla is reduced. 



