Ill 



CRUSTACEA. 



PART II.-PORCELLANOPAGURUS : AN INSTANCE OF 



CARCINIZATION. 



BY L. A. BORRADAILE, M.A., 



Fellow, Dean and Lecturer of Sehoyn Coller/e, Cambridge ; Lecturer in Zoology in the University. 

 WITH THIRTEEN FIGURES IN THE TEXT. 



The " Terra Nova " Expedition captured off the nortlieru end of New Zealand a berried 

 female specimen* of Porcellanopagurus. Although four members of this genus have 

 already been described,! our knowledge of the exceedingly interesting crustaceans 

 which compose it is as yet very incomplete. The " Terra Nova " example (which I 

 have provisionally referred to the type species P. ediuardsi, Filhol) is in rather bad 

 condition, all but the last pair of the legs being detached from the body, while the left 

 cheliped and both legs of the fourth pair are missing. From this specimen, however, it 

 is possible to gather certain facts which have not yet been stated, and to draw certain 

 conclusions. The authorities of the Zoological Department of the British Museum 

 have very kindly afibrded me facilities for examining also two male specimens of 

 P. tridentatus, Whitelegge, from tl^e Kermadec Islands, and for comparing them with 

 various other Paguridea. The following communication embodies the results of my 

 observations upon this material. 



Porcellanopagurus (Fig. 1) is one of the many attempts of Nature to evolve a crab. 

 The material, in this instance, seems to have been an ordinary hermit-crab of the sub- 

 family Eupagurinae, and the method followed was not only, as in other such cases, a 

 broadening and depression of the cephalothorax, as though a weight had been placed 

 upon it, together with reduction of the abdomen, but also a drawing out horizontally 

 of the edges of that hard plate which roofs the forepart of the body of a hermit-crab. 

 This plate is bounded at each side by the front part of the linea anomurica — the " line 



* The specimen is mentioned on p. 97 of the systematic account of the Decapoda collected by the 

 " Terra Nova " (Vol. Ill, No. 2). 



t P. edwardsi, Filhol, 1885; P. platei, Lenz, 1902; P. tridentatus, Whitelegge, 1904; P. japonicus, 

 Balss, 1914. The literature of the genus and its species is as follows : Porcellanopagurus, Filhol, Bull. 

 Soc. Philomath. Paris (7), IX, p. 47 (1885) ; Miss. He Campbell, III, ii, p. 410 (1885). Thomson, Trans. 

 N.Z. Inst., XXXI, p. 187 (1899). Alcock, Cat. Ind. Decap. Crust. II, i, pp. 27, 191 (1905). Chilton, 

 Subant. Is. N.Z., XXVI, p. 610 (1909). Balss, Abh. K. Bayer. Ak. Wiss., math.-phys. Kl., Suppl. II, 

 ix, p. 66 (1913). P. edwardsi, Filhol, Thomson, Alcock, Chilton, ll.c. P. platei, Lenz, Zool. Jahrb. 

 Syst., Suppl. V, p. 740 (1902). P. tridentatus, Whitelegge, Mem. Austral. Mus. IV, p. 180 (1904). 

 Chilton, Trans. N.Z. Inst. XLIII, p. 552 (1911). P. japonicus, Balss, I.e. P. edwardsi?, BoTTudaile, 

 "Terra Nova" Nat. Hist. Rep., Zool, III, No. 2, p. 97 (1916). 



E, 



