394 



descriptions of six new species of australian 

 polyplacophora (four acanth och ito ns and two 

 Callistochitons), with other Notes. 



By Edwin Ashby, F.L.S., M.B.O.U. 



[Read October 9, 1919.] 



Plates XLI. and XLII. 



ACANTHOCHITON PILSBRYI, SykeS. 



PI. xli., figs. 1 to 3. 



A. pilsbryi, Sykes: Proc. Mai. Soc, vol. ii., pt. 2, July, 1896. 



A. maughani, Torr and Ashbv : Trans. Rov. Soc. S. Austr., 

 vol. xxii., 1898. 



I am indebted to Mr. James A. Kershaw, of the National 

 Museum, Melbourne, for the opportunity of examining Sykes' 

 type of the above shell. Sykes states that he had only the 

 single specimen and did not disarticulate the anterior valve. 

 An examination of the type at once gives the reason, for that 

 valve, in common with several of the others, is badly broken. 

 Further, the marked character of the sculpture of this shell is 

 much obscured in the type owing to erosion and fracturing, but 

 still more to the extensive limy encrustations, the deep inter- 

 spaces between the pustules being in most cases entirely filled 

 in with the accretions. 



The very faulty drawings and description in Sykes' paper 

 are undoubtedly due to this feature. Both Mr. Sykes and 

 Dr. Pilsbry, to whom he submitted the type, emphasize the 

 character of the dorsal area, 

 narrow and well denned, but 

 both ignore the characteristic 

 feature of the shape and 

 arrangement of the general 

 sculpture so striking in good 

 specimens of this shell. 



Description of sculpture 



referred to: — In the pleural . - 7 7 ,, -, , 



,, , r , A. pusbryi. method or 



area the pustules are about sculpture in pleural area, 



twice as long as broad, are 



square-ended and set in rows on the diagonal, so that one 

 corner only reaches the upper line, the interspaces between 

 the rows being a series of almost square hollows, the direction 

 of the row of pustules is parallel with the dorsal area. A 

 limited amount of bridging connects the pustules of one row 

 with those of the next row. In the lateral area the row 



