1922.] S. Kemp : Notes on Crustacea Decapoda. 123 



the species of Palaemonclla bear an exceedingly close resemblance to 

 those of Periclimenes. The only valid distinction between the two 

 lies in the presence of a mar iibular palp in the former genus and 

 its absence in the latter. Unfortunately this character is one to 

 which attention is seldom paid, with the result that the generic 

 position of a number of species is doubtful. 



Palaemonclla laccadivensis Alcock and Anderson does not 

 possess a mandibular palp and is transferred to the genus Pericli- 

 menes; in Periclimenes pottsi on the other hand this appendage is 

 present and the species is in consequence removed to Palaemonella. 

 Borradaile's Palaemonella tridentata is in my opinion a synonym 

 of Dana's P. tenuipes and Zehnt ner's Palaemonella amboinensis is 

 perhaps synonymous with Periclimenes brevicarpalis (Schenkel). 



Several species with the dactyli of the last three legs biungui- 

 culate have been referred to Palaemonclla, but the position of all 

 is uncertain. 1 



The five species that I have myself examined may be distin- 

 guished thus : — 



A. Hepatic spine present. 



B. Distal margin of carpus of second leg toothed 

 or angulate on its inner aspect, but without a large 

 siibter initial spine. 



C. Antennal scale strongly narrowed distal ly, 



with spine extending Far beyond apex ; a spine 



at distal end of merus of second leg. 



D. A vestigial supra-orbital spine ; propodus of 



third leg at most 4/5 times length of dactyl us ; 



R. 6-8 : 1-3 ... ... ... vestigial is, sp. nov. 



D' . No vestige of supra-orbital spine ; propodus 

 of third leg more than 5 times length of 

 dactylus; R. 7 : 2 ... ... ... pottsi (Borr. ). 



C. Antennal scale not narrowed distally, with 



spine scarcely extending beyond apex ; no spine 



at distal end of merus of second leg; R. 8 : 3 ... lata, sp. now 



B'. A large subterminal spine on carpus of second 



leg [antennal scale narrowed distally, with spine 



extending much beyond apex ; a spine at distal 



end of merus of second leg] ; R. 6-8 : 1-3 ... tenuipes Dana. 



A'. Hepatic spine absent [no spine at distal end of 



merus of second leg] ; R. 6-7 : 1 ... ... orien talis Dana. 



Palaemonella vestigialis, sp. nov. 



(Plate III, fig. 2.) 



The rostrum extends beyond the end of the antennular pe- 

 duncle and reaches about to the apex of the antennal scale. It 

 varies somewhat in depth and is straight for the greater part of its 

 length with the terminal portion sometimes turned a little upwards. 

 On the upper border it bears from 6 to 8 teeth/ usually 7 ; the pos- 



1 A specimen from Australia which Balss (K. Svenska Vet.-Akad. Hand I. 

 LXI, no. 10, p. 13, 1921) has doubtfully attributed to Nobili's Pnlaemonelln 

 biunguiculata bears only four spines at the apex of the telson and probably be- 

 longs to the subfamily Palaemoninae. 



2 Of thirteen specimens four have 6 dorsal teeth, six have 7 and three have 8. 



