158 
G. W. Lee — Trepostomata. 
Weills is not considerable, and was interrupted periodically at long intervals, so that 
the swellings are few and elongated. The axial portion had to be left unstudied, owing 
to lack of material. The original wall-substance is decomposed, having become white 
and amorphous ; in tangential section the walls appear structureless and the acanthopores 
are unrecognizable. 
' Distribution .—The holotype is from the Lower Limestone of Cookstown, Ireland,, 
and occurs in a red argillaceous limestone containing Foraminifera, a Rhynchonellid, a 
Productus allied to P. elegans M‘Coy, and a species of Aclisina. 
At the time of writing, no other specimens referable to this species have come under 
notice. 
Comparable species. —The tabulation of the peripheral region is a good diagnostic 
character. Of the species which in this respect resemble Stenopora dubia , the undescribed 
specimens from Lydstep Quarry [Pr. 8482-3, see p. 154] differ in having much thicker 
practically unbeaded walls and fewer tabulae. In Stenopora castletonensis sp. nov., from 
the “ Brachiopod-bed ” of Treak Cliff, Castleton, Derbyshire, the tabu he are fewer and the 
beading of the walls is closer, while the zooecia are also much smaller. 
Observations. —The type-specimen of Stenopora dubia is preserved in the Griffith 
Collection, National Museum of Ireland, Dublin. Grateful thanks are due to Dr. R. S. 
Scharff, without whose courteous help it could not have been possible to elucidate the 
systematic position of M £ Coy’s species. 
Stenopora castletonensis sp. nov. 
Plate XV, figs. 9, 10. 
Description. —(a.) External characters. . In the specimens that have come under 
observation the zoarium is composed of solid, cylindrical dichotomous branches 2 to 7 mm. 
in diameter. The surface features are not shown. There are some fifty-five tubes along 
a distance of 1 cm. 
(b.) Internal structure. As seen in longitudinal sections, the proximal ends of the 
zooecia are, as usual, thin-walled. At a point situated below the surface at a distance 
equal to one-fourth of the diameter, they suddenly assume the thick walls characteristic 
of the group, and a direction perpendicular to the surface. The thickening is periodically 
interrupted and the moniliform structure is characteristic’ the inner beads being short 
and close, the outer ones long and tapering. The thickness of the walls is generally 
