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 setae, 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. ungulatus 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. 



