546 REPORT—1904. 
FRIDAY, AUGUST 19. 
The following Papers and Reports were read :— 
1. On the Structure of the Silurian Ophiurid Lapworthura Miltoni. 
By Professor W. J. Sotias, /.R.S. 
The structure of the arms and jaws of this fossil were described from informa- 
tion obtained by a study of serial sections, and reconstructions built up from these 
were exhibited before the Section. 
2. The Base-line of the Carboniferous System round Edinburgh. 
By B. N. Peacu, LL.D., P.RS., and J. Horne, LL.D., FBS. 
In the last edition of the Geological Survey map embracing the Edinburgh 
district (Sheet 32), published in 1892, strata of Upper Old Red Sandstone age are 
represented as occupying the area that stretches southwards from the Castle by 
Morningside and Newington to the Lower Old Red Sandstone volcanic rocks of the 
Blackford Hill and Braid Hills. The rocks consist of conglomerates, red sand- 
stones, marls, and cornstones. The correlation of these strata with the Upper Old 
Red Sandstone was based, not on fossil evidence, but partly on their lithological 
characters, and partly on the fact that along their eastern margin they pass con- 
formably upwards into the Cementstone group of the Carboniferous system. 
The Cementstone group as developed in the Edinburgh district consists of 
grey, green, and red mudstones, and shales with cementstone bands, occasional 
sandstones, and rarely some thin seams of dark carbonaceous shales yielding plants, 
ostracods, and Paleoniscid fish-scales of undoubted Carboniferous type. 
In the last edition of the Edinburgh sheets all the beds between the Castle and 
the voleanic rocks of Arthur’s Seat were included in the Calciferous Sandstone 
series. Our colleague, Mr. Goodchild, however, suggested that the sandstone 
underlying the dolerite sill of Salisbury Crags is of Upper Old Red Sandstone age 
in virtue of the cornstone associated with it, which in the Edinburgh district 1s 
characteristic of that formation. During the revision of the Carboniferous area 
round the city, Dr. Peach recently detected minute fragments of fishes in this 
sandstone where it is exposed at the side of the Queen’s Drive. These were ex- 
amined by Dr. Traquair, who considered them to be fragments of dendrodont 
(Holoptyehian) teeth, though not specifically determinable. Permission having 
been granted by H.M. Office of Works in Scotland to charge the rock exposure 
with dynamite, a mass of material was set free, which, when broken up by the 
fossil collectors, Messrs. MacOonochie and Tait, yielded conclusive fossil evidence. 
After examination Dr. Traquair determined a number of specimens of teeth and 
scales which undoubtedly belong to the genus Holoptychius, a characteristic Upper 
Old Red Sandstone form. Accepting this determination, it is obvious that the 
cementstones to the west must be faulted down against the Upper Old Red Sand- 
stone of Salisbury Crags. 
Attention was next directed to the Craigmillar sandstones lying to the north 
of Arthur’s Seat, and hitherto grouped with the Carboniferous formation by the 
Geological Survey. Mr. Tait here obtained a number of very fragmentary fish- 
remains, one of which, according to Dr. Traquair, is an unmistakable fragment of 
a scale of Holoptychius. Therecan be no doubt, therefore, that the Craigmillar 
sandstones are also of Upper Old Red Sandstone age, At Raeburn’s Brewery, not 
tar trom Duddingston Station, they are overlatd by dark shales and sandstones, 
“with a thin eoaly seam full of plant remains of Carboniferous type. 
Thereatter a special examination was made of the sections north and south of the 
Warklaw Hill, four miles south-west of Edinburgh, which is formed of Lower Old 
Red Sandstone volcanic rocks, where conglomerates, pebbly sandstones and corn- 
stones rest unconformably on that platform, and are overlaid by the Cementstone 
croup. After careful searching by Mr. Tait, fish fragments were found which Dr. 
