STUDIES ON THE CYCLOSTOMATOUS BKYOZOA. 



By Ferdinand Canu, 

 Of Versailles, France, 



AND 



Ray S. Bassler, 

 Of Washington, District of Columbia. 



During our studies of the North American Early Tertiary cyclo- 

 stomatous Bryozoa, published as a part of our monograph of 1920,^ 

 we had occasion to extend our researches to many additional species, 

 both living and fossil, for purposes of comparison and in order to 

 test our classification. Our efforts were particularly directed to 

 specimens bearing ovicells, as it is upon the function of reproduction 

 that our classification is based in part. Species showing no ovicells, 

 however, were also studied, often by means of thin sections, to de- 

 termine the method of gemmation and the occurrence and variation 

 in structure of the several kinds of adventitious and accessory tubes. 

 Our notes upon these additional specimens contain so many new 

 observations upon both described and undescribed species that we 

 thought it advisable to publish them in a series of papers under the 

 above general title. 



1. FOSSIL AND RECENT PARALLELATA AND RECTANGULATA. 



We have found Waters' two subdivisions of the Cyclostomata, the 

 Parallelata, and Rectangulata to be not only convenient but valuable 

 in classification. The present paper deals with both recent and fossil 

 species of the Parallelata and Rectangulata genera listed on the fol- 

 lowing pages. A second paper now in preparation, discusses the 

 Lower Cretaceous Cyclostomatous Bryozoa from the two classic 

 localities, Farringdon, England, and Sainte Croix, Switzerland. 



The researches herein recorded were made possible through a 

 grant from the American Association for the Advancement of 

 Science, for which assistance we are highly grateful. 



1 1920, Canu and Basaler. North American Early Tertiary Bryozoa, Bull. 106 U. S. 

 National Museum (2 vols.), 879 pages, 162 pis. 



No. 2443— Proceedings U. S. National Museum. Vol. 61, Art. 22. 



1 



