ASHBY : NOTES ON THE GENUS STENOCHITON. 265 



Stenochiton (Zostericola) pilsbryanus, Bednall. 

 {=S. pilsbryanus, Bednall, of Ashby, Trans. Roy. Soc. of S. Austr., 

 vol. xliii, 1919, pp. 66-9, pi. xi, figs. 2a-c.) 



The sub-genus Zostericola, Ashby, was made for the reception of 

 this short and broad Stenochiton, whereas all the previously known 

 forms are very much elongated and proportionally narrow. In 

 common with all the other members of this genus, its shell is smooth, 

 highly polished, and practically without sculpture, and it lives on 

 Zostera and Posidonia. Up to the present only two specimens have 

 been recorded : — the adult type collected by the late Professor Ralph 

 Tate and described by the writer, and a juvenile specimen was taken 

 and described by the writer (loc. cit., p. 69). 



The convex character of the anterior valve and the proportionally 

 greater width of the shell separates this species from its congeners. 



VOL. XV.— OCT., 1923. 18 



