PLATE XXI°. 



Brissus carinatus, /. 1-3. 



1. Seen from above, denuded. 



2. Same, in profile. 



3. Same, seen from the actinal side. 



Metalia stern alls, /. 4-S. 



4. Seen from the abactinal pole, 



5. Seen from the actinal side. 



{All Figs, two thirds natural size.) 



