xlii 
INTRODUCTION. 
The Geological Value of the Bryozoa. 
The final test of the classification of Bryozoa depends on 
materials to be collected by the stratigraphical geologist, hut he 
will probably find his trouble repaid by the geological value of 
the Biyozoa. The view was once prevalent that their specific 
life was so prolonged that they would be of no help in zonal 
palseontology. This idea was natural amongst pioneers in the 
description of this group, such as Laraouroux, since they were 
naturally impressed by the few most conspicuous features and 
practically ignored anything less striking than characters of generic 
value. The specific characters were duly recognized by d’Orbigny, 
von Hagenow, von Reuss, and most of their contemporaries; but 
in later years there has been an attempt to return to the pre- 
d’Orbignyan methods. Thus Hincks, by ignoring differences 
between fossil and recent specimens, often included Cretaceous 
and living Bryozoa in the same species. Mr. Waters is now 
the chief upholder of this method, and he has included some 
Carboniferous Bryozoa in living species. 
In recent years the stratigraphical value of the Bryozoa has, 
however, been widely recognized. In the first volume of this 
Catalogue I went much further than most students of Bryozoa at 
that date (1899), but apparently I did not go far enough. Thus 
I suggested, though doubtfully, placing a note of interrogation 
before the name in the synonymy, that the Heocomian Berenicea 
flalelliformis and the Senonian B. gracilis of d’Orbigny might be 
the same species.^ M. Canu^ emphatically rejects this view as 
a simple blunder, and separates the two forms specifically. After 
another ten years work on the Bryozoa I am disposed to regard 
them as better zonal guides, and to look with even greater 
suspicion on the identity of Bryozoa from widely separated 
geological horizons than I was in 1899. 
Of course it may not he possible to separate specifically small 
fragments or imperfectly preserved specimens of Bryozoa any more 
than it is with fragments of other groups of animals ; but that is 
no reason why Cretaceous and living Tholoporce, for example. 
^ B.M. Cat. Cret. Bry. vol. i. p. 73. 
2 Canu, 1902. Bry. foss., I. Coll. Campiche : Bull. Soc. geol. Fr. ser. 4, 
vol. ii. p. 10. 
