162 G. W. Lee — Jrepostomata. 
surface are characters obtaining also in the previous species, from which it differs by the 
above noted features. 
Observation. —The holotype is preserved in the collection of Dr. A. Vaughan, to 
whom grateful thanks are due for allowing sections to be made from it. 
Genus Tabulipora Young; 1 
Section A :—Species in which the perforation of the tabulae occupies a central or sub¬ 
central position. 
Tabulipora scotica sp. nov. 
Plates XIV, figs. 4 A—4 D ; XV, figs. 12, 13, 17, 18. 
Description. —(a.) External characters. The zoarium consists of solid cylindrical 
dichotomous branches from 2 to 7 mm. in diameter. There are some forty apertures along 
a distance of 1 cm. Their partitions are rather thin and somewhat raised, and their out¬ 
line sub-polygonal. A cell smaller than the average occurs sometimes between the larger 
ones. With a strong lens an acanthopore can be seen at each of the junction-angles. 
There are no monticules, but maculae of small cells are common. 
(b.) Internal structure. Longitudinal and transverse sections show that the peripheral, 
thick-walled portion of the zooecia is at right angles to the surface. The walls, which as 
usual are very thin in the axial region, are in the peripheral region about half as thick 
as the diameter of the zooecial cavity. Usually they exhibit a distinct moniliform structure, 
there being as a rule some four or five swellings ; but certain specimens not unfrequently 
evince a decided tendency towards the formation of uniform walls, both beaded and 
unbeaded walls co-existing in the same section. The tabuke bear a central perforation 
the shape of which is somewhat reniform. The margin of the perforation is usually raised 
proximally, appearing in section as a short projection pointing downwards. The size of 
the perforation is equal to about one-third of the diameter of the tabula. The ratio of 
axial region to diameter is equal to 0 - 6 : 1. 
In tangential sections a small acanthopore can generally be seen at the junction- 
angles. Besides, there are often numerous small dark spots, irregular in outline, arranged 
either in sporadic groups or in straight lines. A black line, which may be due to the 
merging of these black spots, sometimes occurs between adjoining zooecia. 
1 A description of the genus is given on p. 149. 
