188 STALK-EYED CRUSTACEA. 



midway between the anterior mai'gin and the cervical groove, at a rather 

 hio^her level than the antenual spine, a lateral spine on the posterior edge 

 of the cervical groove a little lower down than the antennal spine, and an- 

 other (the branchiostegal spine) at the anterior end of the cervical groove, 

 just behind the antero-lateral margin of the carapace. The antero-inferior 

 anufle of the carapace is not armed with a spine. The antennular flagella are 

 missing ; the prosartema is somewhat longer and narrower than in P. dio- 

 medece. The antennal scales are broad and foliaceous. The antennal flagella 

 are more than twice the length of the body. The terminal segment of the 

 mandibular palpi is elongated and much narrower than the preceding seg- 

 ment, but neither segment is so narrow as in P. diomcdece. The legs do not 

 differ in any important regard from those of P. diomedece save that the 

 exopods attain a greater development ; on the second maxillipeds the exo- 

 pods are equal in length to the meri, while on the succeeding pairs of 

 appendages these organs, though small, assume macroscopic proportions even 

 unto the posterior thoracic legs. The number and arrangement of the gills 

 are expressed by the following table : — 



19 + (7) 



It thus appears that the most important structural differences between 

 P. diomedece and P. ocidaris are these : the strong emphasis of the branchio- 

 cardiac groove in the former species, together with the smaller size of the 

 exopods of the maxillipeds and legs, the presence of a minute branchial 

 plume on the seventh (first maxillipedal) somite, and the position of the 

 lowest of the spines on the side of the carapace which in P. diomedecB is 

 marginal, but in P. ocidaris lies a little way behind the margin. It docs not 

 seem to me that the.se differences are of sufficient weight to be esteemed of 

 generic value. 



In all important structural characters, including the disposition of the 

 gills, Pcncopm agrees with Huliponis. The latter genus may be conveniently 

 retained, however, to include the soft-shelled species with long abdomen and 

 long posterior legs. Pleoiiais Bate * docs not seem to be sufficiently distinct 



• Rep. Clialleiigcr Miicrura, ji xii. = Pliiloiiicus Bale, op. ci/., ]^. 273 (iiom. pnroc). 



