PREFACE. 
This volume includes the descriptions and illustrations of the Corals and 
Bryozoa of the Lower Iielderberg group; of the Bryozoa proper, and allied 
forms, from the Upper Helderberg and Hamilton groups. 
When the study of the Broyzoa was begun, the plan of the author con¬ 
templated the production of a work, as complete as possible, to illustrate the 
structure and relations of this class of fossils from the Lower and Upper 
Helderberg, the Hamilton and Chemung groups. With this object in view, 
extensive collections were made from all accessible localities. The drawings 
were commenced and carried on in accordance with this plan, and the better 
specimens for the illustration of the Genera and Species were figured, while 
awaiting other collections to supplement the incomplete material already 
possessed. In this manner some of the groups (or genera) have been very fully 
illustrated, while others, for want of better material, have been less completely 
represented. 
Although considerable collections had been made in preceding years, it was 
not until 1874 that the author, with the assistance of Mr. 11. P. Whitfield 
prepared preliminary descriptions of most of the Corals and Bryozoa of the 
Lower Helderberg group, at that time known to us; which were published in 
the Twenty-sixth Report of the State Museum of Natural History. At a later 
date, while the drawings for the illustrations of these species were in progress, 
and after their completion, a careful review and revision of the species pre¬ 
viously described, and of the new material in hand at that time, was made by 
