137g Prof. H. A. Nicholson’s Contributions 
The nearest allies of Callopora nana, so far as I know at 
present, are C. (Heterotrypa) O’ Nealli, James, and C. (Hetero- 
trypa) nodulata, Nich., both of which are found in the Cin- 
cinnati group of North America. From both of these forms, 
however, the present species is distinguished by well-marked 
external and internal peculiarities, its distinguishing features 
being its small dimensions, the proportionately large size of 
the corallites, and the peculiar elongated form of the inter- 
stitial tubes, while a marked internal feature is the very ex- 
tensive development of the tabule in not only the peripheral 
but also the axial region of the corallites. 
Formation and Locality. Wenlock Limestone, Benthall 
Edge; Wenlock Shales, Buildwas. 
4. Callopora Fletcheri, EK. & H. (PI. VII. figs. 5-5 6.) 
Monticulipora Fletcheri, Edwards & Haime, Brit. Foss. Corals, p. 267, 
pl. Ixii, figs. 3, 3 a, 
Corallum ramose, of cylindrical branches, which have a dia- 
meter of from a line anda half to two lines and a half. There 
are no proper monticules or macule; but the surface shows 
the approximately circular apertures of the ordinary corallites, 
the diameter of which is about 7, mch. ‘The corallites are 
separated by interspaces of from y+, to yz5 mch in diameter, 
and in badly-preserved specimens these interspaces either 
appear as solid or show only here and there a minute poly- 
gonal opening. On the other hand, in well-preserved ex- 
amples the intervals between the ordinary corallites are seen 
to be wholly occupied by the openings of interstitial tubuli. 
In tangential sections (Pl. VII. fig. 5 a) the corallites are seen 
to be thick-walled and circular, with a well-defined internal 
boundary, though not showing the peculiar dark marginal 
ring which is so characteristic of many species of Callopora. 
Occasionally minute tooth-like processes, which look like 
septa, project into the visceral chamber, though I have never 
seen more than two or three of these in a single corallite. 
The walls of the corallites are amalgamated with those of the 
interstitial tubes, and there is rarely more than a single row 
of the latter, while in places the corallites are actually in con- 
tact. The interstitial tubes are rounded or polygonal, and 
only rarely have an elongated form. In long sections (Pl. VIL. 
fig. 56) the ordinary corallites are seen to be provided abun- 
dantly with complete horizontal tabulze, both in the axial and 
the peripheral region of the corallum. As they proceed out- 
wards from the centre to the circumference of the branches, 
they bend at a considerable angle, and their walls become at 
the same time considerably thickened. The interstitial 
