REVIEWS 261 



North American Early Tertiary Bryozoa. By Ferdinand Canu 

 and Ray S. Bassler. United States National Museum, Bull. 

 No. 106, 1920. Pp. 878, pis. 162, figs. 279. 



This monograph forms a pioneer work in the field of American 

 bryozo5logy. Despite the great abundance and splendid preservation 

 of bryozoa along the Atlantic and Gulf Coast regions, there has hitherto 

 been so little done with them as to leave the field almost virgin. 



Under the term Lower Tertiary the authors have included the 

 Midwayan, Wilcoxian, Claibornian, Jacksonian, and Vicksburgian 

 formations. There is found here a much richer bryozoan fauna than in 

 the succeeding formations. A study of the Miocene, Pliocene, and 

 Pleistocene bryozoans has been completed and it is hoped that it will 

 soon appear as a monograph supplementing the present work. An 

 extensive table showing the geographic and stratigraphic distribution of 

 the different species is given. 



Tertiary bryozoans are so intimately related to living forms that a 

 thorough knowledge of the taxonomy and anatomy of living species is 

 necessary for the proper classification and interpretation of the structures 

 found. Accordingly the authors have produced a monograph which is of 

 use both to the zoologist and to the paleontologist. Numerous text 

 figures are introduced to make the report of value to the non-specialist. 

 A detailed discussion of the structure and classification of living forms is 

 given. 



With the exception of one undetermined species, referred to the order 

 Ctenostomata, all Tertiary bryozoans belong either to the Cheilostomata 

 or Cydostomata, the latter being about half as numerous as the former. 

 These are included in the subclass Gymnolaemata, which includes all 

 fossil bryozoans, and is characterized by a circular row of tentacles 

 surrounding the mouth. It is in turn incorporated in the class Ectoprocta 

 which is distinguished by the presence of the anal orifice outside the 

 row of tentacles. 



The Cheilostomata which were probably derived through the Paleozoic 

 Trepostomata, differ from the Cydostomata in that they may be either 

 calcareous or chitonous, and the aperture is closed, upon the retraction 

 of the polypide, by an operculum. The Ctenostomata are chitonous 

 or gelatinous forms with the aperture closed by a tooth-like process. 



The studies of the authors have led them to discard for the present 

 the former major classification of the Cydostomata, retaining for con- 

 venience only the two larger divisions the Ovicellata and Inovicellata. 

 In classifying the Cheilostomata orders were based upon general mor- 



