PLATE XXI. 



FIGS. 



15. dona intestinalis (Linn.) Flem. (p. 9) 1 and 2. Test 

 (1, fully expanded; 2, slightly contracted). 3. 

 Test of a young individual. 4. Branchial aperture. 

 5. Part of branchial sac : magnified. 



6-8. dona pulclwlla Alder, (p. 14) 6. A group of indi- 

 viduals with test extended. 7. A single individual 

 with test contracted. 8. Mantle. 

 9. Corella parallelogmmma (Miill.) Hanc. (p. 25) Test. 



All the figures, except 5, natural size. 



