EXPLANATION OF PLATE XXXIII. 



Fig. 11. Left valve, interior of T. tiui.niun var. /V^v.vo/-, from Lord Howe 

 Island, 195 mm. long. 



,, 12. Left valve, interior of Ctirditu criiS''lcost((, Lamarck, from Anson 

 Ba}', Nortliei'n Ten-itory, 75 mm. long, for comparison 

 with Fitr. 11. 



