PLATE XXI. 



PAGE 

 Fig. 1 . POLYPOEA GRACILIS, PfOUt 422 



1. Natural size. 



1 a. Enlargement of poriferous side. 



Fig. 2. Cyoi.opoba discoidea, Prout. (See also, pi. xxii, fig. 10, 10 a). . .420 



2. Side view of a specimen, natural size, covered by the sole or epitheca 



of the under side. 



2 a. Enlargement of poriferous surface, as shown by removal of a portion of 



the sole. 



Fig. 4. Polypoba Halliana, Prout 421 



4. View of poriferous side, natural size. 

 4 a. Same, magnified. 



4 b. Enlargement of the opposite side. 



Fig. 5. Ctolopoea poltmoepha, Prout 421 



5. Non-poriferous side, natural size. 



5 a. Same, magnified. 



5 b. Poriferous side, magnified. 



Fig. 6. Poltpoea uamiltosensis, Prout 423 



6. View of under side, natural size. 



6 a. Magnified view of opposite side, showing the pores. 



