64 STALK-FA-ED CRUSTACEA. 



readily distinguished from the hitter 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 antennular peduncle, etc. 



Pylopagurus afflnis Fax. 

 Plate XII., Fig. 2-2\ 



Bull. Mus. Comp. Zool., XXn. 169, 1893. 



This species is nearly related to P. wigulahis, from which it differs in the 

 fdllowiu"' respects : the eye-stalks 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. tmrpihttts this face of the carpus is thickly 

 covered with spinulous granules which assume larger proportions and a uni- 

 serial arrangement on the superior and inferior margins. On extending the 

 comparison to the large chela, further differences between the two species 

 become apparent. In both species the external foce is flat, covered with 

 minute spinulous granules, and surrounded by a border of sharp spines ; but 

 in p. affinis the marginal spines are larger and more irregidar, and the flat 

 opercular facet is not sharj)ly defined at the proximal end by the regular 

 arrangement of the marginal spines as in P. wigiilafus ; instead, one finds the 

 marginal series of spines broken down at this point, thus effacing any distinct 

 limit between the opercular face of the chela and the articular surface which 

 connects the propodite with the carpus. The inner or lower surface of the 

 large chela is smooth in P. affinis, granulated in P. wirjnlahis. The left cheli- 

 ped is ([uite different in the two species : in P. affinis the several segments of 

 which it is composed give rise to long setce which give the appendage a 

 very hairy appearance when contrasted with P. xmgnlatus ; 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. ungu- 

 lalut, 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 P.affnm is symmetrical, subcircular in outline, its posterior border 

 convex and entire ; in P. ungulatus, the telson has a deep and wide posterior 

 median notch. 



