PORCELLANOPAGURUS— BORRADAILE. 121 



pairs of legs take part in holding the shell in position. Speculation as to how 

 this may be done, and whether their scaly pads are used for the purpose, does 

 not at present seem likely to be profitable. The eggs, which are of rather small 

 size (-5 mm.) in my specimen, must pass into the deep furrow on the ventral side 

 to which I have already alluded. Thence they must by some means, perhaps by 

 the last pair of legs, be transferred to the back and attached to the hairs of the 

 abdominal limbs. The mass which they then form is moulded to the shape of the 

 covering shell. 



The species of Porcellanopagurus have as yet been very inadequately described for 

 systematic purposes, with the exception of P. tridentatus, of which Whitelegge's 

 account is full and good. This member of the genus differs from the rest more, as it 

 seems at present, than they do from one another. It is smaller, measuring 10 mm. in 

 length, whereas the others probably all reach a length of 15 mm. or more. Its scaly 

 sculpture is finer and its hairs shorter, the lobes of its carapace-edge are less marked, 

 and probably its great chela has a more swollen hand. P. plaiei and P. japonicus, to 

 judge by the figures of them which have been published, lack the third cusp of the 

 second carapace-lobe and have the point of the third lobe more forwardly directed than 

 in P. edwardsi. P. japonicus has a small, sharp spine at the tip of each of the lobes, 

 which is wanting in Lenz's figure of P. ptlatei, and the two species difiJ'er also in the 

 greater smoothness of the legs of the latter. I have already alluded to the question of 

 the abdominal limbs. The " Terra Nova " specimen agrees pretty well with the 

 descriptions of P. edwardsi, but its great chela shows considerable unlikeness to that of 

 the male of Filhol's species as described and figured by Chilton. The scales on the 

 wrist are coarser and less regular, the upper edge of the palm has a well-marked, 

 though irregular, crest of sharp granules or teeth, and along the lower edge there runs 

 a strong, regular line of fine granules. This is evidently also present in P. japonicus. 

 Possibly, however, these differences are sexual, and in any case the examination of 

 a series of specimens would be necessary before a new species could be established for 

 the form taken by the " Terra Nova." 



Porcellanopagurus is a quite independent case of the phenomenon which may be 

 called " carcinization," and which consists essentially in a reduction of the abdomen of 

 a macrurous crustacean, together with a depression and broadening of its cephalo thorax, 

 so that the animal assumes the general habit of body of a crab. To this end, by 

 devious routes, evolution has proceeded throughout the Anomura. In the lower 

 members of most divisions of that tribe the abdomen is a strong and important organ, 

 and the cephalothorax little, if at all, depressed. Their higher members are " crabs." 

 Among the Paguridea, the widening of the region between the bases of the third 

 maxillipeds of the Eupagurinae may perhaps be regarded as a first step in this 

 direction, the broad-backed Eupagurus splendescens (Fig. 11) represents a further 

 advance, and besides Porcellanop)agurus two other members of the sub-family — Tylaspis 



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