782 THE VOYAGE OF H.M.S. CHALLENGER. 



Palsemon longirostris comes from the mouth of the Ganges, Palsemon vulgaris, 

 Say, belongs to North America, and Palsemon tenuirostris, Say, to the coast of New- 

 foundland. 



Under the name of Leander Stimpson records several species from the coasts of 

 China and Japan, and one from Australia. 



Palsemon affinis, Milne-Edwards (PI. CXXVIII. fig. 5). 



Palemon affinis, Milne-Edwards, Hist. Nat. Crust., torn. ii. p. 391. 



Palsemon affinis, Dana, U.S. Explor. Exped., Crust., p. 584, pi. xxxviii. figs. ba-g. 



Closely resembles Palsemon squilla of Fabricius (the Cancer squilla of Linnaeus and 

 most European authors), and only appears to be recognisable from that species in having 

 the apex of the rostrum bifid and four teeth instead of three on the under margin. The 

 specimen from which Milne-Edwards denned the species was not sufficiently preserved to 

 enable him to give a complete description. But Dana has been more fortunate and says 

 that "Although very near to the P. squilla, the coalesced flagella of the inner antennas 

 are united to a longer distance from the base of these organs." 



Habitat. — Port Jackson, Sydney, June 1874. Sixteen specimens; eight males and 

 eight females, the latter bearing ova. 



The carapace is less than one-third the length of the animal, it is crested over the 

 frontal region and anteriorly produced to a rostrum that is equal to the length of the 

 dorsal surface of the carapace, bifid at the apex, and armed on the upper margin with 

 seven teeth, the posterior being on the gastric region and the anterior a little distance 

 from the apex, and on the lower margin with four teeth, the distal being the smallest 

 and nearer the apex than the corresponding tooth on the upper margin. The orbit is 

 defined by an angle on the inner side of the first antennal tooth, below which on the 

 receding frontal margin stands the second antennal tooth ; the surface of the carapace is 

 otherwise smooth. 



The pleon is dorsally rounded and laterally compressed, the third somite, being 

 slightly arcuate, projects posteriorly above the fourth, which with the two succeeding is 

 considerably narrower in the female. The sixth somite is but little longer than the 



