154 
G. W. Lee — Trepostomala. 
Longitudinal and transverse sections, and fractured specimens, show that the ratio of 
axial region to the diameter of the branch is invariably equal to O’7 : 1 (rounding off 
the second decimal), whatever the size of the branch. 
As seen in tangential sections the acanthopores are not very conspicuous. Both 
sets are somewhat irregularly represented, even in the restricted area of a single section. 
The large ones, occupying the junction angles of the zooecia, are deep-rooted and are 
consequently observable in sections cut a considerable distance below the surface. The 
smaller ones, numbering at most ten to each zocecium, are confined to the outer layers of 
the peripheral region, and may easily be unrepresented in a given section, if the latter is 
cut too deep. 
The main diagnostic features of the species are the ratio of the axial region to the 
diameter, and the localisation of the tabulae in the sub-peripheral region. 
Distribution. —This species, as delineated here, is abundantly represented in the 
Redesdale Ironstone shale, at Redesdale, Northumberland, where both the solid and hollow 
types of branching co-exist. It is also very common at Bellingham and Lewisburn, from 
which localities only solid branches have been observed, and at Clattering Ford, Cumber¬ 
land, where hollow branches only have so far been obtained. It occurs also at two other 
localities in the Bewcastle district. In Scotland it occurs at Lawston Linn, Liddisdale, 
and at Arbigland. These localities lie approximately on the same horizon near the 
middle of the Yisean. The first of these occurrences and that at Lawston Linn have 
been assigned to the D1 zone by Mr. Stanley Smith and Dr. A. Vaughan respectively. 1 
Comparable species. —Forms possibly allied to Stenopora redesdalensis , but too 
insufficiently represented to warrant a separate description, occur in the South-West 
Province. In the Geological Survey Collection there are two specimens [Pr. 3482, 
Pr. 3483] from Lydstep Quarry, 3 miles W.S.W. of Tenby, Pembrokeshire (upper 
sub-zone of Seminula ), which have a general resemblance to Stenopora redesdalensis , but 
differ from it in being thicker-walled and in having a few tabulae in the peripheral region. 
Specimen Pg. 1824, from a cliff about 235 yards S.E. of Stackpole Quay, Pembroke¬ 
shire, in beds doubtfully referred to the lower sub-zone of Seminula , has a similar 
tabulation, but its walls are thicker and uniform, and its acanthopores appear to be of 
one size only. Stenopora dubia (M’Coy) from the lower Limestone of Cookstown, 
Ireland, is distinguished by the close tabulation of its peripheral region. A specimen of 
37, 46. 
