vine: YORKSHIRE CARBONIFEROUS AND PERMIAN POLYZOA. 197 
The distribution of this species, so far as I am aware, is rather 
more restricted than the fomier, R. gnicile, as I have not met with 
examples either in Wales or Derbyshire, but I should not like to say 
that it is absent from these places. Otherwise I have nearly always 
found B. rhombiferum wherever R. gracih was fairly abundant. 
In looking over the figures of Phillips, in Geology of Yorkshire, 
and ticking off his very brief description, I think it no detriment to 
the author to say that as Phillips speaks of M. rhomh'ifera only, in all 
probability that which passes now as R. gracile in the Yorkshire 
rocks, was non-existent at the time he wrote. The distinction 
between the two species being unknown, or at least unrecorded, 1 
believe that the name Millepora rJwmbifem covered the now, two 
distinct species. We owe to the letter of Phillips''' to the Messrs. 
Young, of Glasgow, the statement, Your examples are better than 
mine were, but I have no doubt of the reference. The difference of 
opposite faces of C. or Rh. rkomhifera is very interesting," a possible 
confirmation of this view. The ovicells of this species are most 
peculiar. One of the best I have figured (pi. vii., f. 5), and it will be 
seen to be entirely unlike any of the ovicells described in the first 
part, or on the present memoir. In itself it is a perfect study. The 
form is a sac (elongated oval ?) tapering, or rather thinning out 
towards the apex, in which is a small orifice, but there is no secondary 
opening in the sac. Surface of the ovicell much roughed by delicate 
wart-like prominences, which give to the surface a peculiar granular 
appearance. This, however, is in keeping with the granulation which 
is seen occasionally on the surface of the vestibular area just below 
the spines which ornament the walls of the same. On the side of the 
ovicell the Zooecial apertures are slightly altered in appearance, but 
they are not, so far as I can see, pushed out of position much. As 
ovicells of Rhahdomeson rhombiferum are very rare, I hope, now that 
I have directed attention to them, workers will look out for ovicells of 
R. gracile as well. 
Section B. Zooecia radiating in all directions round an imaginary 
axis. 
Genus Rhombopora, Meek. 
1871. F. B. Meek, Paleeontology, Eastern Nebraska. 
^ Ann. Mag. Nat. Hist., 1875, p. 334. 
