268 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 18 



Telson moderately broad, apices rather narrow, notched, armed with 

 a stout spine or spines; subterminal dorsolateral edges each armed with 

 a spine or groups of spines. 



Third epimeron : posterior edge nearly straight and distally setose, 

 lower corner quadrate or slightly produced. 



Remarks. — Despite the considerable differences in the figures con- 

 cerning the three species which have been fused here, no consistent quali- 

 tative differences can be pointed out. The published figures of P. robusta 

 and P. milleri are males, the former an immature one; P. longirostris is a 

 female (being half as large as P. robusta) or possibly a juvenile, for the 

 spines and setae on its peraeopods are not as richly developed as in the 

 other two representatives. The material at hand comprises a number 

 of specimens of all ages. 



This species is characterized by the stoutness of the fifth article of 

 the fifth peraeopod, occurring in all three representatives. The coxal 

 cusps shown so well developed by Miss Thorsteinson are not quite as 

 well represented in the material at hand but are evident in figures of 

 P. robusta and only slightly in P. longirostris. The third uropods of 

 the male representatives compare well, being characterized by the 

 shortness of the second article of the outer ramus. 



The general shape of peraeopod 5, article 2, and its teeth are similar 

 in all but P. longirostris, which is probably an underdeveloped juvenile, 

 although the shape of the appendage is similar. The telsons vary in shape 

 and spination from animal to animal but no clear demarcation among 

 them is apparent. All the telsons correspond to the extent of bearing 

 short spines, no long setae. 



The gnathopods show many agreements, particularly in the length 

 of the fifth article, but Miss Gurjanova's drawings of her two species 

 do not show the clear contrast between the convex anterior and straight 

 posterior edges of the sixth article seen in P. milleri and the specimen 

 at hand. This is also true of the transversity of the palms of the American 

 specimens. 



The dorsal shape of the heads corresponds less well than other 

 characters, but this problem may be resolved in part by different aspects 

 and mounting techniques used. The rostrum in P. robusta appears broader 

 than in specimens at hand or P. longirostris but the difference is so small 

 that it can be attributed to intraspecific variation. The process on the 

 lower corner of the head in P. robusta, figured as a large cone, I attribute 

 to the possible exaggeration of the gland cone on the second antenna, 

 which appears more rounded in Thorsteinson's drawing of P. milleri. 



