I 



575 



I. contractus, Rv. Tlie synonymy is given by Iredale and 

 May (Proc. Mai. Soc, vol. xii., pts. ii. and iii., Nov., 1916) 

 as follows: — I. contractus, Rv., 1847; C. sidcatus, Quoy et 

 Oaim., 1834, non Wood, 1815; C. decussatvs, Rv., 1847; 

 <C. castus, Rv., 1847; Lepidopleurus speciosiis, Ad. and Ang., 

 1864; Gymnoplax nrviUei, Rochebr. , 1881. 



Plaxiphora (Chiton) hiramosa, Quoy et Gaim., 1833. 

 Type, New Zealand (Voy. de I'Astrol., iii., p. 378, pi. 74, figs. 

 12-16). This specimen is very badly eroded, showing no 

 sculpture, only a few zebra-like markings on a brown ground. 



Plaxiphora f Chiton' alhid/us) alhida, Blainville. Type, 

 He King (Diet. Sc. Nat., vol. xxxvi., p. 547, 1825). There 

 are six valves in tub© marked type, M3 36a,' anterior, pos- 

 terior, and four median valves. These were disarticulated 

 by Dr. J. Thiele, and, as stated by him, are very bleached and 

 •eroded, but one of the valves shows distinct wrinkling, and 

 all show, near margins, growth-lines and the usual, although 

 faded, green and brown dashes or bands. 



Plaxiphora (Chiton costatus) costafa, Blainville. Type, 

 Port du Roi George (Diet. Sc. Nat., vol. xxxvi., p. 548). The 

 ■specimens, which are dissected, are also labelled "Chaefo- 

 jpleura costata, Bl." This is the usual ribbed and wrinkled 

 forjn oi Plaxiphora found in South Australia. The anterior 

 -diagonal rib is well defined and a large portion of it smooth ; 

 the posterior margin of the median valves is not well defined. 

 The wrinkling is very marked in zigzags. The usual green 

 ►colour markings are present. 



Plaxiphora (Chiton f/laucus) rjlauca, Quoy et Gaim. 

 Type, Van Diemen (Voy. de I'Astrol. ZooL, iii., p. 376, 

 t. 74, f. 7-11, 1834); marked in (Quoy or Gaimard's) hand- 

 writing as from Van Diemen. There are only four valves, 

 which belong to the smooth form, w^ithout wrinkles. I have 

 similar specimens from Tasmania. The shell is~a good deal 

 •eroded, but there is sufficient to show that, when perfect, it 

 was unwrinkled. 



Comment. — Dr. Thiele quite correctly recognized de 

 Blainville's C. cosfatus in the wrinkled form of Plaxiphora, 

 ranging from Victoria to Western Australia, wliich appears 

 to have been described by Sowerby under the name of P. 

 petholafa- But he concluded that the bleached and eroded 

 specimen described by Blainville under the name of C . alhidus 

 must be the smooth form described by Quoy et Gaim. under 

 the name of C. r/lauc{/s. The discovery of defined wrinkling 

 on one of the valves of Blainville's type of C. alhidus dis- 

 proves this. I am satisfied that his alhidus and costatus are 

 conspecific, the former being a worn and bleached specimen of 

 \ the latter. As alhidus has page priority'-, it must stand as 



