164 
G. W. Lee — Trepostomata. 
Tabulipora youngi sp. nov. 
Plate XY, figs. 19, 20. 
Description .—(a.) External characters. The zoarium consists of solid cylindrical 
branches from 2 to 6 mm. in diameter. About forty sub-polygonal or sub-circular 
apertures are found along a distance of 1 cm. Specimens which agree in their internal 
structure show differences in the thickness of the partitions of the apertures, which tend 
to be circular, the thicker their partitions. In the forms with thick partitions some ten 
small acanthopores encircle the aperture. 
(b.) Internal structure. In the peripheral region the diameter of the walls is 
approximately equal to that of the zooecia, and is uniform throughout. Some five 
tabular, with reniform central perforation, generally occur in the peripheral region, where 
the distance separating them is approximately equal to their own diameter. Tabulae are 
scarce in the axial region. The ratio of axial region to diameter is about 0*5 : 1. 
Tangential sections show that the acanthopores are not so regularly distributed as one 
might infer from the surface characters. Numerous dot-like acanthopores(?) occur 
between a larger set generally localised in the junction-angles. 
Distribution.—Tabulipora youngi has been found at a number of Scottish Lower 
Limestone localities. It is not yet known from other horizons or from localities outside 
Central Scotland. 
Observations. —The sections figured in pi. xv., figs. 19, 20, belong to a slide 
preserved in the Young Collection, Kelvingrove Museum, Glasgow, labelled |^01 — 53 ~j 
with the name Tabulipora urei (Flem.). 
The ratio of axial region to diameter, and the considerable thickness of the walls, 
readily separate T. youngi from other Scottish species. 
Tabulipora minima sp. nov. 
Plate XY, fig. 21. 
Description. —(a.) External characters. The zoarium consists of small solid 
cylindrical branches from 1 to 2 mm. in diameter. As this species is usually indifferently 
preserved it is not possible to state whether maculse and monticules are present. There 
are about forty apertures along a distance of 1 cm. Both circular and subpentagonal 
apertures can be seen on the same zoarium. A row of minute acanthopores can just be 
seen with the help of a strong lens. 
