336 BULLETIN 93, UNITED STATES NATIONAL MUSEUM. 



CATOPHRAGMUS POLYMERUS Darwin. 

 1854. Catophragmus poly merits DARWIN, Monograph, p. 487, pi. 20, figs. 



Type. British Museum, from Twofold Bay, New South Wales. 

 Richmond, near Melbourne, Victoria, on shells and stones, collected 

 by Mrs. Agnes Kenyon. The shape of the opercular valves varies a 

 good deal. In low, spreading individuals the scutum is broad, as 

 figured by Darwin, but in high ones with steep walls it is narrower, 

 the basal margin shorter than the tergal, and the articular furrows 

 of both valves are more oblique, so that the articulating borders are 

 much less deeply notched than Darwin's figures show. It appears to 

 be a strictly littoral species, living with Tetraclita, Chthamalus, etc. 



