G. RB. VINE ON CRETACEOUS LICHENOPORIDA. 851 
RaDIOPORA PUSsTULOSA, d’Orb. 
=f. pustulosa, Vine, B. A. Rep. 1883,=? R. bulbosa, d’Orb. Pal. 
Frang. Terr. Cret. Tome v. p. 996. 
1. Superficial Zoaria.—If we examine any ordinary specimen of 
R. pustulosa, which I believe is rather common in the Lower Green- 
sand of Faringdon; we shall find that the exposed surface is composed 
of a series of undulating or mamilliform prominences which are 
very characteristic. A mere superficial examination of these mamille 
will show that they are slightly rayed, and that the interspace 
between one mamilla and another is filled in by an apparently loose 
cancellous texture. If the apices of these prominences are slightly 
rubbed down and then examined under a low power of the 
microscope, the rayed character of the series of cells is distinctly 
visible. A better process, however, is to break from the fossil small 
fragments and then prepare and mount them as transparent objects. 
In these sections the structure of this species may be advantageously 
studied, and it is from specimens thus prepared that the following 
observations are made. 
2. Massive Colonial Growth.—The massive growth of R. pustulosa 
is peculiar. The multiform zoaria are built up of a series of 
apparently laminated layers, of varying thickness; but on the average 
four of these layers measure about half a line. There is, however, 
a longitudinal as well as a superficial section which must be studied 
if the details of the building-up of massive forms of the fossil Polyzoa 
are to be mastered. In the longitudinal section of R. pustulosa 
before me there are about thirty of these layers. Towards the base 
of the fossil the disks, which will be described presently, are few 
in number, probably three or four ; but of the primary disk I cannot 
speak. This simple layer, which may be conveniently spoken of as 
the originating layer, is composed of confluent disks, which appear to 
have had a limited range superficially. 
The upward building of colonial growths began at the edges of 
the originating layer, whence fresh or newer zoaria gradually spread 
and consolidated over the first-formed as well as over successive 
layers ; but the disks did not always anastomose at the edges, like the 
disks of var. a (meandrina, Peach), previously referred to. Many of 
them remained free, while others were connected, in part, by what 
appears to be cancellous tissue. This, however, I believe to be a de- 
ceptive feature; for in all probability what we suppose to be cancelli 
are only the broken edges of the tubular extensions of disk and disk. 
In some sections of the fossil a peculiar overlapping may be seen, and 
even the beginning of anew disk which will become proliferous on its 
near neighbour. This “ overlapping,” too, gives rise to a peculiar 
structure of the longitudinal section. In the general building up 
of the zoaria of this species 11 may be noted that the mamillz 
in each succeeding layer are immediately above the mamille below, 
and not covering up interspaces or previously formed zoaria 
discrimininately. I cannot tell the why or the wherefore of this ; 
