G. W. Lee — Trepostomaia. 
165 
(b.) Internal structure. In most instances the thick-walled peripheral end of the 
zooecia is not at right angles to the surface, but falls on it somewhat obliquely. The 
thickness of the peripheral end of the walls is approximately equal to one-third of the 
diameter of an average zooecium. Perforated tabulae are present throughout the course 
of the zooecia, but are more abundant in the peripheral and sub-peripheral regions, where 
the distance separating them is usually less than their own diameter. They are thick, 
with a well marked proximally raised margin round the perforation. The ratio of axial 
region to diameter is 0'6 :1. Tangential sections show a moderately large acanthopore at 
most of the junction-angles. Besides, in shallow sections, adjoining zooecia are separated 
by a row of minute black dots, which, when close together, appear as a black line. 
Distribution. —Small branches presumably belonging to this species are often found 
in the Scottish Lower Limestones, but since they are usually too imperfectly preserved to 
permit of correct identification, it is advisable to mention here only the locality from 
which tolerably good specimens were obtained, namely, Howood Quarry, Renfrewshire. 
Observations. —The materials on which the above description is based are represented 
by seventy-eight sections on three slides preserved in the Young Collection and labelled 
“ Tabulipora urei small var.” x ^ ^ ^ ° y ^ J all from Howood Quarry. 
The section figured in pi. xv., fig. 21, belongs to the last of these slides. 
Note on the Trepostomata of Central Scotland. 
Besides the three species described above, the Young Collection contains a fourth, 
to which a separate description is not allotted here, since it seems to be very rare. It is 
depicted in pi. xv., fig. 11, and the original is one of eight sections on a slide ^ J 
labelled, like the preceding species, with the name Tabulipora urei (Flem.). The locality 
is Trearne, Beith, Lower Limestones. The specimen has an oval section, but this is not 
due to crushing. The centre is obscured by infiltrated matter, and has been left blank in 
the figure. The chief distinguishing characters of this species are the small proportion of 
the axial region relatively to the diameter, and the slender walls and close tabulation of 
the zooecia in the peripheral region. A specimen [25572] resembling this one in its 
proportions, but differing in having less distinctly beaded walls, was obtained by 
Mr. Rhodes from an old quarry N.E. of Bowsden, If miles N.W. of Lowick, Northumber¬ 
land (see pi. xiv., fig. 6). With so little material at hand it is not possible to say whether 
