96 
Genus BOTRYLLOPORA (Nicholson). 
(Canadian Journal, Vol. XIV., No. 2, 1874.) 
Polyzoary calcareous, sessile and encrusting, forming systems of small circular dises, the 
upper surfaces of which are marked with radiating ridges upon which the cells are carried. 
Each disc is attached by its entire lower surface, slightly convex above, with a central non- 
poriferous space, round which a number of radiating poriferous ridges occupy an exterior 
slightly elevated zone. Cells forming a double series on each ridge, immersed, with rounded 
mouths which are not elevated in any part of their circumference above the general surface. 
I have been unable to refer these singular Polyzoa to any existing group, and have, 
therefore, been compelled to form a new genus for their reception. In some respects the 
genus is allied to Defrancia, but the cells are not tubular, and no portion of them is free, 
whilst the latter genus does not appear to have ever been detected in rocks older than the Ju- 
rassic. The only Paleeozoic genus of Polyzoa which, so far as I am aware, presents even a 
superficial resemblance to Botryllopora, is Evactinopora of Meek and Worthen. In this latter 
genus the polyzozry is star-shaped, but its internal structure is quite peculiar and altogether 
different to that of Botryllopora, whilst the entire organism appears to have been free. 
The individual dises of Botryllopora present, however, a very striking resemblance to the 
separate star-shaped elevations of Stellipora antheloidea (Hall), from the Lower Silurian ; and 
it may, therefore, be proper to say a few words on the structure and affinities of this genus, 
of which | have examined authentic specimens. Stellipora antheloidea occurs in the form of 
flattened expansions or of erect, flattened and sub-palmate fronds. The surface exhibits a vast 
number of little star-shaped elevations, each about a line in diameter, and consisting of a 
smooth, sometimes slightly depressed space, which is traversed by five, six or more obtusely- 
rounded radiating ridges, which do not quite meet in the centre. Hach of the ridges of the star 
is covered with a number of rounded calices, irregularly disposed in two,three or four rows. The 
stars are arranged irregularly, gencrally at intervals of from half a line to a line, and the inter- 
spaces between them are occupied by crowded circular pores, which are the mouths of so man 
coenenchymal tubuli. These pores do not encroach upon the spaces between the ridges of the 
stars, and the tubuli of which they are the mouths are seen on traverse section to be tabulate, 
being furnished with distinct transverse partitions. It thus appears that Stellipora antheloidea 
(Hall), is not a Polyzoén, as believed by D’Orbigny, but a tabulate coral, allied to Monticuli- 
pora, and presenting in particular a specially close resemblance to the coral which I have 
described under the name of Callopora incrassata. 
117. BorryLLoPpora socrAuis (Nicholson). 
Botryllopora socialis (Nicholson), Geological Magazine, April, 1874. 
Polyzoary social, consisting of systems of calcareous discoid bodies, which are closely 
adherent by their lower surface to the exterior of foreign objects. The upper surface of each 
dise is on the whole convex, but with a central cup-shaped depression or flattened space, the 
exterior portion of each being occupied by a series of strong elevated ridges or ribs arranged 
in a radiating manner, The diameter of the discs is about a line or aline and a quarter, and 
the radiating ridges are from eighteen to twenty-six or more in number. The radiating ribs 
ave also unequally developed, some extending much nearer to the centre than the others, and 
each carries upon its upper surface a double row of minute round pores or apertures, the margins 
of which are not elevated above the general surface. The central space of the polyzoary is des- 
titute of cells, and appears to be solid, and this seems also to be generally the case with the 
ee spaces between the radiating ribs. In some cases, 
» - however, the interradial spaces appear to be poriferous 
=> in the immediate vicinity of the circumference. 
¢ The groups of this singular Polyzoin are not of 
very rare occurrence in the Hamilton formation, 
growing parasitically upon the exterior of Heliophyl- 
Fig. 32. lum Halli. It has at first sight, a close resemblance 
a, Portion of ‘a coral with a small group of Botry?. tO a group of little discoid corals, such as Microcyclus, 
icy sma (Nich ote magna Asusle attached by the whole of the lower surfuce, the cellu- 
ridges, enlarged to show the cells. From the Hamil- liferous ridges looking just like the septa, and the 
sa ae central space resembling the bottom of the calice. I 
