395 



becomes curved and the pustules larger, more raised, and 

 rounded. 



Hab. — Victoria and South Australia. 



ACANTHOCHITON PILSBRYI MAUGHANEANUS, n. Sp. 



PL xli., fig. 4. 



Differs from A. pilsbryi, Sykes, in having pustules less 

 raised and rounded. The pustules are even more rectangular 

 than is the case in the dominant form ; in the anterior valve 

 they are about twice as long as wide, straight-sided and square- 

 ended, narrower as well as being less raised. While probably 

 the number of pustules is about the same, owing to their being 

 more slender the interspaces are proportionally wider. In the 

 median valves the pleural area is markedly different from A . 

 pilsbryi in that the pustules are very slightly raised, are long 

 and slender, with greater space between the rows. Also the 

 bridging in the species under description is more complete, a 

 raised ridge joining the posterior portion of one pustule to 

 the anterior portion of the corresponding one in the row above, 

 thereby increasing the honeycomb appearance so characteristic 

 of the southern and dominant species. The pustules in the 

 lateral area are more raised and larger than in the pleural, 

 but this feature is less pronounced than in A . pilsbryi. 



Hab. — Sydney Harbour, New South Wales. 



Remarks. — Owing to the recognition of Dr. Torr's and my 

 A. maughani as Sykes' shell, that name becomes a synonym 

 of A. pilsbryi. I am therefore preserving the name of Mr. 

 M. M. Maughan, the ex-Director of Education in this State, 

 by naming the subspecies after him. 



The type I am presenting to the South Australian 

 Museum; it was collected by myself at Middle Harbour, 

 Sydney, New South Wales. 



Genus Acanthochiton, Gray,. 1821. 

 * Subgen. Notoplax porcina, n. sp. 

 PI. xli., figs. 7 to 10. 

 General appearance. — Shell elongated, glossy, carinated, 

 side slope straight, all valves more or less covered with fine 

 longitudinal ribbing. 



Colour and markings. — Light vinaceous-cinnamon, mot- 

 tled with congo pink in the dorsal areas (Ridgway's Colour 

 Standards, pi. xxviii. and xxix.). 



Anterior valve. — Has five shallow undulations or ray ribs, 

 is fairly evenly covered with wavy, concentric ribbing ; in 

 character these resemble "ripple marks" on the sea sand. 

 These marks turn inwards towards the apex of valve along the 

 central rib. Near the apex the "ripple marks" are crowded 



