PLATE XXII. 



Brissus unicolor, /. 1, °i. 



1. Seen from abactinal pole, nat. size. 



2. Seen from actinal side, nat. size. 



Meoma ventricosa, / 3, 4. 



3. Seen from abactinal pole partly denuded, | nat. size. 



4. Seen from aetinal side, | nat. size. 



