118 "TERRA NOVA" EXPEDITION. 



the " Terra Nova" specimen, which is a female. Filhol, describing what may have been 

 either a male, or a female deprived of her egg-bearing limbs, mentions a pair of small 

 appendages on the forepart of the abdomen, presumably on the first abdominal segment, 

 though they do not appear in his figure. Lenz even figures such limbs in P. jylatei, of 

 which his specimens were females. I am unable to find any traces of appendages in 

 this position in the " Terra Nova " specimen, nor are they mentioned or figured by any 

 other author. Probably they do not exist.* In Eupagurus this segment is without 

 limbs in either sex : in various other Eupagurinae it bears them, sometimes in the 

 female, sometimes in the male. The limbs of the second, third, and fourth segments of 

 the female Porcellanopagurus (Fig. 10«) resemble those of the same sex of Eupagurus 

 (Fig. 106) in being biramous, and in the shape of both branches, but not in the size of 

 the exopodite, which is so minute that the limb appears at first sight to be uniramous. 

 Outside (that is, above) the exopodite, the end of the protopodite has a strong, blunt 

 angle, upon which is a bunch of long hairs, whose function is to supplement those of 

 the endopodite in bearing the eggs. The position of these limbs is interesting. They 

 are all dorsal, and the first is almost median : the other two lie successively more to the 

 left, so that the three form a slanting row. Here is a reminiscence of the relation which 

 the same appendages bear to one another in an ordinary hermit-crab, where, although 

 they lie directly one behind the other if the abdomen be untwisted, yet in its normal 

 spiral position they form a row slanting to the left. In correspondence with this is the 

 fact that in Porcellanopagurus the exopodite, which stands in front of as well as above 

 the endopodite in the limb of the second segment, is more dorsally placed in that of the 

 third, and directly above the other branch in that of the fourth segment, and thus has 

 in each case the position which it would have if the abdomen were spirally twisted. It 

 would appear, therefore, that the secondary straightening of the al^domen of Porcellano- 

 piagurus has been brought about by a process of telescoping rather than by untwisting, 

 so far as the greater part of its length is concerned : the telson and sixth segment have 

 to a considerable extent been rotated backwards into their original position. That the 

 limbs are more dorsal in position than usual, is no doubt in connfection with the manner 

 in which the abdomen is protected, and serves to bring the eggs under shelter of the 

 shallow shell which the animal carries over its back. I have been unable to find in this 

 genus any trace of the little appendage which is borne on the fifth abdominal segment 

 in Eupagurus. 



The only male Porcellanopagurus which I have been able to examine is that of 

 P. tridentatus. In it the abdomen bears no limbs on any segment but the sixth. 

 This is a sharp distinction from some species of Eupagurus, but not from others. 



* It is not clear that Filhol is not alluding to the limb of the second abdominal segment, or even to 

 the last thoracic appendage. Lenz's figure is probably very inaccurate. I have already stated that it 

 omits the antennal exopodite. It also shows a pair of appendages in the first abdominal segment, but 

 none on the second, third or fourth. If these be not serious errors, P. platei differs very remarkably from 

 the other species of the genus to which it has been assigned. 



