G. W. Lee — Trepostomata. 
161 
Stenopora tenuipora sp. nov. 
Plates XIV, fig. 10 ; XV, figs. 6, 7. 
Description. —(a.) External characters. In the single available specimen of this species 
the zoarium is composed of a solid cylindrical dichotomous branch 3 mm. thick. The 
surface is even, there being neither maculae nor monticules. The apertures, numbering 
some eighty along a distance of 1 cm., have thin partitions, and are polygonal in 
outline. They are generally of sub-equal size, only a few being distinctly smaller than 
the average. An acanthopore occurs at most of the junction-angles. The fractured 
ends of the zoarium expose the casts of the zooecial tubes, which are seen to reach the 
surface at an acute angle, without a sharp bend. 
(b.) Internal structure. In longitudinal sections the zooecia-walls are seen to curve 
gently towards the surface. At a distance from the surface equal to about one-sixth of 
the diameter, they assume the usual thickening, which is not very considerable, the 
thickness of the wall being generally somewhat less than one-third of the diameter of the 
zooecial cavity. The walls show no indications of beading, but they are markedly flexuous. 
Tabulae are generally confined to the peripheral region where as a rule less than six 
are visible, separated by intervals which may be less than their own diameter. Very few 
tabulae occur in the axial region. A peculiar feature observed in two of the sections 
prepared, is that in many instances the tabulae appear to be much thicker proximally than 
distally. The ratio of axial region to diameter is equal to about O’7 : 1. Tangential 
sections exhibit clearly one of the most characteristic features of the species, namely, the 
polygonal shape of the zooecial tubes, which, as already stated, is also shown by the 
apertures. A fairly large acanthopore, often with a distinct central lumen, generally 
occurs at the junction-angles. From this description it will be seen that the aspect of 
a tangential section is very much like that of the surface. 
Distribution. —The specimen described here was collected by Dr. A. Vaughan from 
the basement beds,(Kl) of the Lower Carboniferous in the Avon section, Bristol. [Since 
the above passed into the press, specimens referable to the same species have been 
observed in a fragment of limestone from Hook Point, Wexford]. 
Comparable species. —The extreme tenuity and the polygonal shape of the apertures 
and zooecia of Stenopora tenuipora distinguish it readily from the other Stenoporae 
described in this contribution. Flexuous walls and zooecia falling obliquely on the 
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