43 



at botli sides a radial rib above which more or less vertical 

 zio--zasr striae are visible." He adds that Blainville's shell 

 "is said to have come from King George Sound." He goes 

 on to give the result of his examination of the type of Chiton 

 alhidus, Blain., "which originated from King Island, south 

 of Australia." His reference to the sculpture is as follows: — 

 "A definite radial rib is not in evidence, only a blunt ridge, 

 having at one place, in the front, a few zig-zag indentations," 

 and adds, "I was unable to examine the original of Plaxi- 

 phora glauca, Quoy and Gaim., from Tasmania; according 

 to the drawings it would be possible to class it with the last- 

 named species, though the colour is somewhat different." 

 Without going into the question as to how the mistake 

 occurred, it is quite evident that the words quoted from Dr. 

 Torr's paper transpose Dr. Thiele's statement, and the shell 

 that has been referred £o by Torr and quoted by Hedley (in 

 Jour. Roy. Soc. W. Austr., vol. i., 1914-15, p. 23) as P. 

 costata, Blain., must in future be designated P. albida, 

 Blain. 



The shells collected by myself at Cottesloe and Dongarra 

 vary considerably; all but one show a single diagonal rib 

 and some are quite free from wrinkling or notching, but 

 others show a slight wrinkling, and one, if held in a certain 

 light, shows distinct raising of the posterior margin of the 

 central valves, suggesting a second diagonal rib so common 

 in the strongly sculptured specimens of P. petholata, Sow., 

 which equals P. costata, Blain. 



The limit of the present paper prevents the discussion 

 being carried further. Either we have been confusing three 

 species and one sub-species under the name of P. petholata, 

 Sow., and P. glauca, Quoy and Gaim., or these three forms 

 are referable to one very variable species and possibly one sub- 

 species, viz., P. conspersa, Ad. and Ang. 



Kopionella matthewsi, Ire. — Three specimens of this in- 

 teresting shell were found at Yallingup. All show similar 

 ^oar-headed spicules" to the South Australian form which 

 was fully described in my paper (Trans. Roy. Soc. S. Austr., 

 vol. xliii., 1919), and a like slight cleft in the girdle behind 

 the tail valve. 



The writer has now found members of this genus from 

 eastern Tasmania to the west coast of Western Australia, 

 and in every specimen the strange "oar-headed spicules" are 

 present. All specimens I have collected, even when separated 

 by more than a thousand miles, are invariably furnished with 

 these spicules. 



