1912.] S. Kemp & R. B. S. Sewell : Notes on Decapoda, III. 17 



Aristaeus semidcntatus, Bate. 



Aristaeus semidentaius, Alcock, 1901, p. 31, and ///. Zool. Invest., 



Crust., pi. xlix, fig. 3. 

 } Aristeus semidentaius, de Man, iQir, p. 29. 



Six males and eleven females were obtained at St 391. 

 They agree precisely with Alcock 's account and with other speci- 

 mens in the Museum collection. The pleurobranchs in advance of 

 somite xiv are the merest rudiments, minute papillae without 

 trace of pinnae. 



It would appear doubtful whether the specimens obtained 



by the ' Siboga ' really belong to this species, for de Man states 



that the pleurobranchs above the base of the first four peraeo- 



pods are "distinct filaments, similar to those of A. virilis" ; 



whereas the difference in this respect between the present 



specimens and the examples which Alcock referred to A . virilis 



is most marked. 



« 



Hemipencus crassipes (Wood-Mason). 



Hemipeneus crassipes, Wood-Mason and Alcock, 1891, p. 281, fig. 

 7; Alcock, 1901, p. 33, and ///. Zool. Invest., Crust., pi. 

 xlix, figs. I, 2. 



A single male, jy mm. in length, was found at St. 388. 



Among the males of this species preserved in the Indian 

 Museum, two different types of modification are observed in 

 the ultimate and penultimate segments of the external maxilli- 

 peds. The differences are shown in pi. i, figs. 8 and 9. In 

 one form (fig. 9), that which is shown in the ' Investiga- 

 tor ' illustrations, the penultimate segment is cylindrical and 

 swollen and the ultimate segment is dilated at the base with 

 the distal part curved outwards and provided with a spatulate 

 tip. In the other type (fig. 8) the penultimate segment is flatter 

 and less swollen and is produced distally as a strong acuminate 

 process in front of the insertion of the ultimate joint. The latter 

 is curved as in the type figured by Alcock ; but it is not dilated at 

 the base. 



It is with the second of these two types that the specimen 

 from St. 388 corresponds, and it is possible that the form deserves 

 recognition as a distinct variety. The material at our disposal 

 is not, however, in good condition and we are content to leave 

 the matter pending the acquisition of further specimens. 



Aristaeomorpha rostridentata (Bate). 



Aristaeus {Aristaeomorpha) rostridentata , Alcock, 1901, p. 39, and 

 ///. Zool. Invest., Crust., pi. ii, fig. i. 



Two males, obtained at St. 391, unquestionably belong to the 

 same species as the female example recorded by Alcock and Wood- 

 Mason under the name of A. rostridentata, and there can be 



