852 G. R. VINE ON CRETACEOUS LICHENOPORIDA. 
but the fact being known, the study of a single colony or disk will 
be less puzzling to future students. 
Fig. 1. —Sections of the zoariwm of Radiopora pustulosa, d’Orb. 
Enlarged. 
A. Transverse section of the disk ; a. Celluliferous centre; . Tubular cells cut 
at different angles, sloping upwards towards the margin of the disk. 
B. Longitudinal section of some of the marginal cells. 
3. Zoarial Disks.—It is almost impossible to break off from the 
fossil a fragment too small to show a single disk at least. Generally 
speaking two or three may be secured. I have drawn, with the aid 
of the camera lucida, a transverse section of one of these disks 
(fig. 1, A). In the central part (a) there is a kind of cancellous 
structure, which appears to me to be nothing more than the cut 
ends of the tubular cells. These are contiguous, many-shaped, 
but more frequently circular or hexagonal, and the wall of each is 
distinct. ) 
In the outer region of the disk (6) the circle is composed of long, 
tubular zocecia which radiate from the axis. The zocecia are also 
contiguous by their walls, but in some places these are separated by 
slight division; but I have no evidence of cancellous interspaces, as 
in some of the Discoporelle, or even as in Radiopora simplex, Busk 
(Brit. Mus. Cat. pl. xxxiv. fig. 2). Mr. A. W. Waters, however, has 
identified one of his Bay-of-Naples Polyzoa as R. pustulosa, d’Orb. 
(Ann. & Mag. Nat. Hist. April 1879, p. 277); and as he speaks of 
*‘ cancelli-tubes which in the lower half are divided across the axis 
by septa* [tabulee ?], giving this part a somewhat cellular appearance,” 
it seems to me to be pretty evident that our own Lower-Greensand 
species may be looked upon as distinct from the recent Bay-of-Naples 
* Since the above was written, I find that Mr. 8. O. Ridley (Ann. & Mag. 
Nat. Hist. June 1881, p. 452) has drawn special attention to the “septal struc- 
tures in Lichenopora,” in his paper on the Polyzoa of Franz-Josef-Land. 
Assuming that his view may possibly be a correct one (op. cit. p. 453), the 
“septa,” or “tabule” of Polyzoan species may ultimately merit special study. 
