156 



Rapid Bay (Angas), Holdfast Bay (Bednall), and New South 

 Wales (Cox, Brazier). I have specimens dredged by Dr. 

 Verco in Backstairs Passage, and either good specimens Or 

 valves from Cape Jervis, Normanville, Aldinga, and Brighton. 

 The splashes of pink colouring are very vivid when preserved 

 in spirits. The peculiarly large and broad anterior valve 

 easily differentiates this species from L. volvox. It flattens 

 itself so closely to the rocks and is so covered with foreign 

 growth that I have had the greatest difficulty in detecting one 

 on a rock which I had been examining for some minutes. 



Fam. MOPALIID^E, Pilsbry. 



38 Plaxiphora albida, Blainville, 1825. 



Chiton albidus, Blainville, Diet. Sci. Nat., 1825, vol. xxxvi., 

 p. 547; Pilsbry, Man. Conch., 1893, vol. xv., p. 105. 



C. glaucus, Quoy and Gaimard, Voy. " Astrolabe," Zool., 

 1834, vol. iii., p. 376. 



(?JC. petholatus, Sowerby, Mag. Nat. Hist., new series, iv., 

 p. 289, May, 1840; Conch. Illustr., f. 64, 65, and var. porphyrins, 

 f. 59. 



Chcetopleura conspersa, Adams and Angas, P.Z.S., 1864, 

 p. 193; P.Z.S., 1865, p. 187. 



Plaxiphora albida, Blainville : Thiele, Zool. Chun, 1909, Heft 

 lvi., p. 24, pi. iii., figs. 22, 23. 



P. tasmanica, Blainville: Thiele, loc. cit., p. 25, pi. iii., 

 figs. 24-26. 



P. bednalli, Blainville: Thiele, loc. cit., p. 25, pi. iii., 

 figs. 27-30. 



P. petholata, Sowerby: Pilsbry, Man. Conch., vol. xiv., p. 

 323; Bednall, Proc. Mai. Soc, London, vol. ii., part 4, April, 

 1897, p. 154. 



P. albida, Blainville: Iredale, Proc. Nat. Soc, London, vol. 

 ix., part 2, June, 1910, p. 98. 



South Australian chiton-hunters will always be grateful 

 to Mr. Iredale for his elaborate paper on the Plaxiphoras, 

 and to Dr. Thiele for his "Revision des Systems der Chitonen." 

 But we part with the old name of petholata with regret. 

 Sowerby's description of petholata, loc. cit., is a complete 

 account of our albida, while Blainville's description of albida 

 in Pilsbry, loc. cit., is very poor, and might be that of any 

 of our Plaxiphora. Is not there a danger in making the 

 posterior valve the basis of decision 1 I have several hundred 

 specimens of Plaxiphora before me from all parts of Aus- 

 tralia, most of them collected by myself, and the tail valves 

 differ so much in the same species according to size and growth 

 that I agree with Iredale that Dr. Thiele, "through lack of 

 specimens, has laid too much stress upon the value of the 

 shape of the valves." The three South Australian Plaxi- 



