xl 
INTRODUCTION. 
The Cyclostomata seem to have three chief types of zooecia — 
{a) Simple, tubular, monomorphic zooecia, with solid walls. 
(b) Zooecia monomorphic, having walls perforated by cavities — 
the cancelli. 
(c) Zooecia dimorphic, one set being aborted to form supporting 
elements in the zoarium. 
Accordingly, in 1896 in the Museum Catalogue of the Jurassic 
Bryozoa, and in 1899 in the first volume of the present Catalogue, 
I divided the Cyclostomata into three sections, the Tubulata, 
Cancellata, and Dactylethrata, each characterized by one of the 
three types of zooecia. 
The Tubulata seem to form a homogeneous group. The 
Eleidae is its most aberrant family. The other families can be 
divided into two series : those in which the zooecia are combined 
as units; and those in which they occur in bundles, and the 
structure is therefore fasciculate. The opinion that the fasciculate 
arrangement of the zooecia is an important taxonomic character 
has had the support of Mr. A. \V. Waters,^ and has been 
widely accepted ever since d’Orbigny founded his division, the 
Fasciculinh. 
The Cancellata are characterized by their cancelli, whose nature 
has been discussed on pp. xxi-iv. Mr. Waters in 1884 remarked 
that the existence of cancelli “does so far seem a character of 
great value, and these seem to indicate a different origin of the 
zooecial tube.” ^ 
The Dactylethrata prove to be a less coherent group than 
I expected in 1896 ; but the isolation of the families is probably 
due to their specialized structure, for the presence of the supporting 
elements led to the development of large zoaria, which diverged at 
once along very different lines. 
The following is a synopsis of the classifi.cation proposed in the 
two previous Catalogues, as expanded to include the remainder 
of the Cretaceous Cyclostomata, which are described in this 
volume : — 
1 A. W. Waters. Foss. Cycl. Australia: Quart. Journ. Geol. Soc. 1884, 
vol. xl. p. 678. 
2 A. W. Waters. lUd. 
