MUSEUM OF COMPARATIVE ZOOLOGY. 169 
Station 3368. 66 fathoms. 5 males. 
Resembles P. ungulatus (Studer), but readily distinguished from that species 
by the great size of the right cheliped, the irregularly oval outline of the right 
chela, the great length of the distal segment of the antennulary peduncle, etc. 
Pylopagurus. affinis, sp. nov. 
This species is nearly related to P. ungulatus, from which it differs in the 
following respects. the eyestalks are longer, and narrower at the distal end ; 
the external prolongation of the second segment of the antenna is longer and 
slenderer; the upper margin of the carpus of the right cheliped is armed with 
two or three spines, the largest of which is close to the anterior border ; the 
outer face of the carpus is smooth save where a light tubercular ridge runs 
along the middle. In P. ungulatus this face of the carpus is thickly covered 
with spinulose granules which assume larger proportions and a uniserial ar- 
rangement on the superior and inferior margins. On extending the comparison 
to the large chela, further differences between the two species become appar- 
ent. In both species the external face is flat, covered with minute spinulose 
granules, and surrounded by a border of sharp spines; but in P. affinis the 
marginal spines are larger and more irregular, and the flat opercular facet is not 
sharply defined at the proximal end by the regular arrangement of the marginal 
spines as in P. ungulatus ; instead, one finds the marginal series of spines 
broken down at this point, thus effacing any distinct limit between the oper- 
cular face of the chela and the articular surface which connects the propodus 
with the carpus. The inner or lower surface of the large chela is smooth in 
P. affinis, granulated in P. ungulatus. The left cheliped is quite different in 
the two species: in P. affinis the several segments of which it is composed give 
rise to long set, which give the appendage a very hairy appearance when 
contrasted with P. ungulatus ; the inferior border of the chela is conspicuously 
toothed, while in P. wngulatus it is entire. The ambulatory legs are more 
hairy in the Pacific species than in P. ungulatus, and their carpal joints are 
not so distinctly dentate on the superior border. The rasps of the fourth pair 
of legs are multiserial in both species. The telson is symmetrical, subcircular 
in outline, its posterior border convex and entire ; in P. ungulatus, the telson 
has a deep and wide posterior median notch. 
Length, about 12 mm. ; length of carapace, 4.5 mm. 
Station 3397. 85 fathoms. 1 male. 
There are three simple unpaired abdominal appendages on the left side, in 
the type specimen. The vasa deferentia are extruded from the base of the 
fifth legs on each side. They appear as slender threads, the one on the right 
side much longer than its fellow, and twisted into a small bunch. 
