XVII. NOTES ON DECAPODA IN THE 

 INDIAN M U S E Lm . 



I. — The Species of Gennadas. 



By STANI.EY Kemp, B.A., Assistant Superintendent, 

 Indian Museum. 



(Plates xiii and xiv.) 



Among the vast collection of Decapods which has been 

 made by the ' Investigator ' thirteen examples of the genus Gen- 

 nadas occur and, although the majority of these specimens have 

 already been mentioned by Alcock,' it has now become necessary 

 to submit them to revision. In 1901, when Alcock wrote, the 

 characters by which the many closeh'- allied species of this genus 

 were determined had not been fully appreciated and our knowledge 

 of the extra- Atlantic forms was limited almost entirel}^ to the 

 wholly inadequate treatment which vSpence Bate accorded them in 

 his ' Challenger' Report. 



Recently Bouvier has published a most valuable account* of 

 the Atlantic species in which he draws attention to the importance 

 of several characters which had previously been overlooked and, 

 now that the * Challenger ' collections have been revised on the 

 same lines ,^ the determination of the material preserved in the 

 Indian ]\Iuseum presents a task of no great difficult5^ 



In the following descriptive notes all the more important 

 characters suggested bj' Bouvier have been employed. It seems, 

 however, that the Oriental species of the genus form a much more 

 homogeneous group than those found in the Atlantic and, apart 

 from the petasma and thelycum , little can be found which is of 

 real systematic value. Useful indications are afforded by the 

 antennular peduncle, the antennal scale and the second maxilla, 

 but in other respects, such as the proportions of the mandibular 

 palp and the respective lengths of the joints of the first three 



1 Alcock, Desc. Cat. Ind. deep-sea Macrura, 1901, p. 45. 



■?• Bouvier, Res. Camp. Sci. Monaco, fasc. xxxiii, 1908, p. 24. 



■•> Kemp, Pyoc. Zool. Soc, 1909, p. 718. From the list of species of Gennadas 

 given at the end of this paper (p. 728) two Pacific forms, G. clavicarpus and 

 G. pasithea, are unfortunately omitted. Preliminary descriptions of these two 

 species, which were obtained by the ' Siboga ' expedition, have been given by Dr. 

 J. G. de Man (Xotcs Leyden Mns., xxix, 1907, p. 144). Both are, I believe, distinct 

 from the ' Challenger 'species and from those here described, but, until figures of 

 the petasmata and thelyca are published, it is impossible to be quite certain. 



