XXV. NOTEvS ON CRUSTACEA DEC A POD A 

 IN THE INDIAN MUSEUM. 



XIII. The Indian speciks of Macrophthalmus. 



By Stanley Kemp, B.A., Superintendent^ Zoological Survey 



of India. 



Plate XXIV. 



Since Alcock published his account of the Indian species of 

 Macroplithalmus in 1900 ' a considerable amount of additional 

 material has been obtained from various sources. A number of 

 species not hitherto known from Indian waters have been added to 

 the list, while several which were known to Alcock only by name 

 have been rediscovered. 



In determining the species I have derived great assistance 

 from Dr. Tesch's recent monograph of the genus.* This work 

 contains a most valuable key to twenty-five species, critical notes 

 on their characters and synonymy and a great number of figures. 

 I have found myself in complete agreement with Tesch as regards 

 the species recognised by him, but I differ from him, and from 

 other recent authorities also, in my views on the position of the 

 species usually termed Euphx bosci. 



The genus Euplax was established l^y Milne-Edwards for the 

 reception of certain species which he found to differ from typical 

 Macrophthalmus in the squarer outline of their carapace, in their 

 shorter eyestalks and in the shortness of the chelipeds in both sexes. 

 During the sixty years that have intervened since Milne-Edwards 

 wrote, numbers of additional species have been described, referred 

 for the most part to Macrophthalmus, and nowadays it is no longer 

 possible to form two distinct groups on the characters on which 

 he based his generic distinction. 



Tesch, in his account of the Grapsoid crabs collected by the 

 ' Siboga' ex]3edition ^, distinguishes Euplax from Macrophthalmus by 

 other characters : by the extent of the gape between the external 

 maxillipeds and by the proportions of the merus of those appen- 

 dages. In these respects, however, the difference is sometimes so 

 very slight that it is clear that they do not afford a basis for generic 

 differentiation. 



1 .-Xlcock, Joiiru. Asiat. Soc. Bengal, I. XIX, p. 375 (igooi. 

 •2 Tesch, Zool. Medcd. Rijlas Miis. Xaf. Ilisf. Leiden, 1, pp. 149-204, pis. v- 

 ix (1915). 



'i Tesch, Derap. Brachvnr. 'SUmga' E.xped.. XX.XIXc, p. 57 (l()lM. 



