POLYCHELES. 117 
sixth, which ends in an acute spine; their margins are lightly denticulate ; 
the pleure of the second somite have a peculiar shape, their anterior part 
flaring out laterally into an angular wing. 
The chelipeds are rather slender; the merus is very lightly spinulose 
along each margin, and is provided with one or two spines at the distal 
end; the carpus is short and armed with a spine at the distal end of both the 
superior and inferior borders ; the hand is armed with about ten spines on 
the upper margin and is lightly spinulose on the lower margin. Of the four 
succeeding pairs of legs the first three are chelate, while the fourth or pos- 
terior thoracic is not chelate, but ends in a simple dactylus ; all of these four 
pairs are clothed on their outer side with long hairs, and a few slender spines 
are irregularly disposed on the three anterior pairs. 
The first abdominal somite is devoid of appendages in the unique ex- 
ample obtained, which is doubtless immature. The second somite bears a 
pair of long two-branched appendages ; the inner branch supports a slender 
process (stylamblys) on its inner border. The succeeding pairs decrease in 
length. 
Length, 37 mm. ; carapace, 21 X 17 mm.; abdomen, 17 mm. 
Station 3403. 384 fathoms. 1 specimen. 
POLYCHELES He ter. 
Sitzungsber. Kais. Akad. Wissensch. Wien, Math.-Naturw. Cl.., XLV., Abth. I., 389, 1862. 
In 1878 Spence Bate established the genus Pentacheles for the reception 
of several species of Macrura from the “ Challenger” collection, which differ 
in no way from Polycheles except in the chelate structure of the posterior 
thoracic appendages. It has since been shown that in some species these 
appendages are chelate in the female while they are simple in the male; 
that among the adults of those species which have the posterior thoracic 
appendages chelate in both sexes there is a gradual transition from a 
perfect chela to an imperfect one, in which the “thumb” is rudimentary 
and the structure of the appendage closely approaches to that of Poly- 
cheles ; that in species in which the appendages in question are chelate or 
subchelate in the adult male they are simple in small, immature individuals. 
Chelation of the posterior pair of thoracic limbs in this family is not accom- 
panied by any other differences, species which have been assigned to differ- 
ent genera resembling each other so closely in every other regard that they 
