Z BULLETIN 100, UNITED STATES NATIONAL MUSEUM 



Without the generous aid of the Bureau of Fisheries in the preparation 

 and illustration of material and of financial assistance from our friend 

 F. Julius Fohs, of New York City, who has helped us in other works 

 as well, this volume could not have been brought to a successful 

 conclusion. 



The authors are greatly indebted to Miss Jessie G. Beach, of the 

 division of paleontology, who has not only been most active in the 

 translation and preparation of the manuscript, but has assisted very 

 materially in the numerous details which accompany such a work. 

 They are also highly appreciative of the help of Miss Francesca 

 Wieser in the preparation of the many drawings of opercula and other 

 structures throughout this work. In practically all cases these 

 illustrations are based upon actual photographs. 



In our studies of American Tertiary bryozoa ' we took the oppor- 

 tunity of publishing text figures and descriptions of the many families 

 and genera concerned in that work. We have followed this practice 

 in the present report so that in these three volumes a summary of 

 the family and generic characters of most of the Post-Paleozoic 

 bryozoa may be found. We have, therefore, endeavored to make 

 these volumes of service as a guide to the study of the bryozoa in 

 addition to a description of the special faunas considered. Our 

 generic researches which have thus covered the whole field of Post- 

 Paleozoic and recent bryozoa have been made possible through a 

 grant from the American Association for the Advancement of Science. 

 As in the past, we are again very grateful for this assistance in making 

 the classification more available to the student. 



In our monograph on the Early Tertiary Bryozoa of North America, 

 we have given somewhat detailed descriptions of the methods of 

 study and the various structural features as well as the principles of 

 classification of the two predominating Post-Paleozoic orders, Cheilo- 

 stomata and Cyclostomata, so that it is unnecessary to repeat this 

 information at this time. However, a few words as to the preparation 

 of suitable slides of the opercula and chitinous appendages for exami- 

 nation under the microscope are in order. Various methods for the 

 separation of the opercula and other appendages from the zoarium 

 and mounting them properly have been described by the authors, but 

 we have found all of them to be very complicated and time consuming. 

 Our numerous preparations have been made by simply scraping the 

 surface of a few zooecia from the zoarium with a sharp scalpel and 

 gently crushing the material thus obtained in a drop of water on a 

 glass slide. The appendages being flexible are seldom crushed or 

 broken in the process, so after spreading the crushed material in the 

 water and allowing it to dry, Canada balsam and a cover glass are 

 added as usual to complete the mount. 



i North American Early Tertiary Bryozoa. Bull. 106, U. S. National Museum, 1920. North American 

 Later Tertiary and Quaternary Bryozoa. Bull. 125, U. S. National Museum, 1923. 



