72 
BEREXICEA. 
unless the recent and Cretaceous species be worthy of generic 
separation. Dacryopora has been used by Terquein^ for B. archiaci. 
The retention of this genus has been criticized by M. Canu, who 
includes it in Biadopora ; but AI. Canu accepts Prohoscina, which 
appears to me less distinct from Berenicea than the latter is from 
Biastopora. 1\I. Canu^ has also criticized the grouping of the 
Jurassic specimens into ‘species,’ and proposed a ditferent arrange- 
ment based on the dimensions of the constituent elements of the 
zoarium. M. Pergens® in 1895 advocated the use of ilimensions 
for the identification of Bryozoa, and has quotc*d dimensions 
extensively in his valuable “ Revision.” That equivalent zooecia 
in zoaria belonging to different species often differ in size is 
undoubted. But equivalent zooecia in different species, acconling 
to M. Pergens’ own measurements, are often of the same size. 
Difference of size in the zooecia does not appear to be necessarily 
a specific distinction, but to be due to the conditions of growth. 
It is, of course, possible, by the adoption of artificial averages, 
to divide specimens of Berenicea into groups characterized by 
different dimensions; but such groups do not appear natural or 
satisfactory. 
An attempt was made in the Catalogue of Jurassic Bryozoa to 
compare the principal characters of equivalent zooecia in different 
species by the use of formulae ; but the variability of zooecial 
dimensions is so great that even such a generalized use of dimensions 
appears too difficult to yield useful results, aud is accordingly dis- 
continued. In the present volume actual dimensions are given in 
the hope that they will save trouble to those students of the 
Bryozoa who prefer to classify the species according to the size of 
the zooecia. On that system the specimens grouped together as 
Berenicea papyracea, for example, will have to be separated, owing 
to the differences in size stated on p. 77. 
^ Terquem, 1855. Pal. dep. Moselle, p. 26 (of separate copies) ; and 1868, in 
Jacquot, Description geol. dep. Moselle, pp. 290, 296. 
2 Canu. Ovicelles Bry. Bathonien; BuU. Soc. geol. France, ser. 3, vol. xxvi. 
1898, pp. 265-280. 
^ Pergens. Note sur I’identification et la separation des especes dans le 
groupe des Bryozoaires: Bull. Soc. beige Geol. vol. ix., Proc. verb. 1895, 
pp. 8-11. 
