" The suggestion that it may be as well to give up the attempt to define species, 

 and to content oneself with recording the varieties .... which accompany a 

 definable type . ... in the geographical district in which the latter is 

 indigenous, may be regarded as revolutionary ; but I am inclined to think that 

 sooner or later we shall have to adopt i." HUXLEY, 1880. 



PART I. INTRODUCTION. 



1. The Problem of Tubular Fossils. 



2. The Affinities of the Bryozoa. 



3. The Structure of a typical Bryozoan. 



4. The Terminology of the Shells of the Cyclostomata and Trepostomata. 



5. The Value of Generic Divisions in the Cyclostomata. 



1. Simplicity of Structure. 2. The Stomatopora-Diastopora Series. 

 3. Are there any Genera in Cyclostomata ? 4. Circuit. 



6. Specific Groups and Individual Variation. 



1. The Variation of Zooecia. 2. The Comparison of Equivalent Zooecia. 

 3. Variational Formulae. 4. Continuous Variation. 



7. The Classification of the Cyclostomata. 



1. The four orders of Gymnolaema. 2. Previous Classifications. 3. The 

 Classification proposed. 



8. Previous work on the Jurassic Bryozoa. 



9. The British Museum Collection. 

 10. The Jurassic Sequence. 



