258 University of California Publications in Zoology. [Vol. 4 



sesses a functional digestive tract, locomotor organs, and probab- 

 ly certain organs of sense, and is well fitted to live for a relatively 

 long time in the free swimming stage. A well known CypJion- 

 autes of European waters, Cyplionautes conipressus, metamor- 

 phoses into Memhranipora pilosa, a species not as yet reported 

 from these shores. Certain Cyplionautes have been long ob- 

 served in our waters, however, and recently the metamorphosis 

 of one of them was found to give origin to 31embranipora villosa, 

 a species restricted to this coast. 



KEY TO THE SPECIES OF MEMBKANIPOEA. 



1. Zooecia quadrangular, with a spine at each distal angle 2 



1. Zooecia not quadrangular 6 



2. Front wall wholly membranous 3 



2. Front wall not wholly membranous 8 



3. Margins of zooecia raised, narrow 4 



3. Margins of zooecia not raised, not narrow 7 



4. Margins of zooecia smooth M. membranacea 



4. Margins of zooecia more or less serrate 5 



5. Front wall beset with minute spines M. villosa 



5. Front wall not beset with spines M. serrata 



6. Zooecia oval, front wall membranous 7 



6. Zooecia not oval 8 



7. Margin broad, beset with spines M. spinifera 



7. Margin broad, without spines M. lacroixi 



8. Avicularia present 9 



8. Avicularia absent 13 



9. Aperture occupying only part of the front; beset with spines 10 



9. Aperture occupying only part of the front, without spines 



M. sandalia 



10. Ocecia immersed, spines few M. occultata 



10. Ocecia not immersed, spines many 11 



11. Aperture broader than long, spines jointed M. patula 



11. Aperture not broader than long, spines not jointed 12 



12. Zooecia with areolations between them, spines 10-14 



M. clrcumclathrata 



12. Zooecia without areolations between them, spines fewer than 10-14 



M. horrida 



13. Zooecia with thickened calcareous tubercle at each distal angle, 



tubercles confluent in older parts of colony M. tehuelcha 



