42 



and also collected it on the limestone rocks at Rottnest, Don- 

 gara, and Geraldton. Heretofore it has not been recorded 

 further north than Rottnest Island. The northern specimens 

 are much lighter in colour than those from Yallingup, the 

 ground-colour of both being pale "Ochraoeous-Buff" (Ridg- 

 way's Colour Standards, pi. xv.), slightly necked with darker 

 streaks. The more southern shells are much more exten- 

 sively thus flecked, which gives them a greyish look. The 

 reddish form so common in South Australian waters is quite 

 absent. The girdle is banded in a varying degree. The 

 sculpture differs slightly from the eastern shells, the longi- 

 tudinal ribbing of the pleural area is less regular, and the 

 nodules of the lateral area are coarser and suggest often two 

 nodulose, radiating ribs. Should it be desired to distinguish 

 this western variety, I suggest that it be known as var. 

 occidentalis . 



C alii sto chit on meHdionalis, Ashby. — This shell was fairly 

 numerous at Yallingup. It was taken by Torr, in 1910, at 

 the same spot, and recorded by him under the name of C. 

 antiquus, Reeve (Trans. Roy. Soe. S. Austr., xxxv., 1911, 

 p, 98). 



Plaxiphora albida, Blain. — I collected these on limestone 

 rocks both at Cottesloe and Dongarra, in positions exposed to 

 the full force of the waves. Dr. Thiele (Faun. Sudwest 

 Austr., III., 1911, p. 402) records the same shell from Cottesloe 

 under the name of P. albida, and I saw in the Western Aus- 

 tralian Museum a specimen from that locality so' labelled by 

 Dr. Thiele. This form is not the heavily wrinkled one that 

 used to be known by Australian collectors as P. petholata, 

 Sow., but in most cases it corresponds with the non-wrinkled 

 shell we used to recognize as P. glauca, Quoy and Gaim. 



Dr. Torr (in loc. cit., p. 99) identifies this shell as P. 

 costata, Blain., and writes as follows: — "Mr. Iredale says, 

 'Blainville's costatus is easily recognizable as the species I 

 have noted as glauca, Q. et G.' He agrees with Dr. Thiele, 

 in his Revision des Systems der Chitonen, in placing P. 

 petholata, Sow., as albida of Blainville, and P. glauca, 

 Q. et G., as costatus, Blain." 



Up to the present I have with some misgivings been 

 following the course adopted by Dr. Torr. I now* have a 

 translation of Dr. Thiele 's work before me. In it he savs, 

 referring to Blainville's type of Chiton costatus, which he 

 had before him, that it is "probably the one named Plaxiphora 

 petholata by Sowerby (1840); as Blainville's names were pub- 

 lished in 1825, P. costata is certainly older." He then 

 describes the sculpture as follows: — "The central areas have 



