1g12.] S. Kemp & R. B.S. SEWELL: Notes on Decapoda, III. 17 
Aristaeus semidentatus, Bate. 
Aristaeus semidentatus, Alcock, Igo1, p. 31, and Ill. Zool. Invest., 
Crust.; pl. xtix, fig. 3. 
? Avisteus semidentatus, de Man, IQII, p. 29. 
Six males and eleven females were obtained at St 301. 
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 pinna®. 
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. vivilis”’; 
whereas the difference in this respect between the present 
specimens and the examples which Alcock referred to A. virilis 
is most marked. 
Hemipeneus crassipes (Wood-Mason). 
Hemipeneus crassipes, Wood-Mason and Alcock, 1891, p. 281, fig. 
7+ Alcock, 1901, p. 33, and Jil. Zool. Invest., Crust., pl. 
xlixs figs: st, 2: 
A single male, 77 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 pl. i, figs. 8 and g. 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 (Aristaezomorpha). rostridentata, Alcock, Igor, p. 39, and 
Ill. Zool. Invest., Crust., pl. 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. rostvidentata, and there can be 
