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INDIAN MUSEUM. 
I.—THE SPECIES OF Gennadas. 
By STANLEY 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 Igor, when Alcock wrote, the 
characters by which the many closely-allied species of this genus 
were determined had not been fully appreciated and our knowledge 
of the extra-Atlantic forms was limited almost entirely to the 
wholly inadequate treatment which Spence 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 Museum presents a task of no great difficulty. 
In the following descriptive notes all the more important 
characters suggested by 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 
} Alcock, Desc. Cat. Ind. deep-sea Macrura, 1901, p. 45. 
2 Bouvier, Rés. Camp. Sci. Monaco, fasc. xxxiii, 1908, p. 24. 
5 Kemp, Proc. 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 (Notes Leyden Mus., 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. 
