Chap. VIII.] SILURIAN ROCKS OF EDINBURGHSHIRE. 
159 
Upper Silurian Rocks of Edinburghshire. — Eeference has already been 
made to the Silurian rocks of the Pentland Hills. "When the last edition 
of this work was published that portion of Midlothian was under exami- 
nation by Mr. Geikie, in the course of the Geological Survey of Scotland. 
Since that time he has brought to light a large number of fossils which 
place the Upper Silurian character of the deposits beyond question. He 
has also furnished me with the following account of the locality : — 
" During the progress of the Survey of the Pentland Hills I was fortu- 
nate enough to stumble upon a number of beds, among the Silurian rocks, 
charged with well-preserved fossils. An examination of these fossils by 
Mr. Salter showed that many of them were Ludlow species, and that a 
representative of the Ludlow rock had now been detected in a new locality. 
The strata are well seen both on the North Esk and the Lyne "Waters, as 
well as in several smaller burns. Taking the section in the Esk, the fol- 
lowing series in descending order may be traced: — 
" Overlying unconformable conglomerate, greywacke, and trappean rocks, 
belonging to a middle part of the Old Eed Sandstone. Eed Sandstones, 
shales, and conglomerates, marking perhaps the base of the Lower Old 
Eed Sandstone, passing down into : — 1. Olive and brown sandy shales and 
mudstones, often full of well-preserved fossils. Thickness perhaps about 
1000 feet. 2. Hard sandstone and quartzose grit, with Orthonota amyg- 
dalina &c. 3. Olive and brown sandstones and shales, passing down into 
green, grey, and reddish shales, with hard sandstone and greywacke bands ; 
Dictyocaris sometimes abundant. Yisible thickness about 2500 feet, when 
the beds are unconformably overlain by the first-mentioned conglomerates. 
The following are some of the fossils of the upper beds : — 
" Chondrites verisimilis (a true Sea-weed), Amphispongia oblonga, Stenopora fibrosa, 
Favosites alveolaris, Protaster Sedgwickii, Encrinurus, sp., Phacops Stokesii, Pterygotus 
acuminatus, Entomis, Ceriopora granulosa, Atrypa reticularis, Orthis elegantula, Stro- 
phomena applanata, S. depressa, Leptsena transversalis, Orthonota amygdalina, Euom- 
phalus funatus, Orthoceras Maclareni, O. subundulatum, Conularia Sowerbyi. 
" These and other fossils are given in the Appendix to the Memoir on 
the Geology of the Neighbourhood of Edinburgh (Mem. Geol. Survey, 1861, 
p. 132). Since that memoir was published the list has been considerably 
increased, by Mr. G. C. Haswell and other members of the Edinburgh Geo- 
logical Society*. While the upper part of the Pentland section may be 
regarded as of Ludlow age, it is evident that there is room for a represen- 
tation of the Wenlock series also. This is rendered probable by the number 
of Wenlock species which have been obtained from these rocks." 
The Orthoceras here figured (p. 160) was detected by my distinguished 
friend the late Mr. Charles Maclaren, and has been named O. Maclareni. 
It formed part of the collection of the eminent geologist Hugh Miller, 
who lent it to me for publication. 
* See a Memoir by Mr. Haswell on the Pentland Hills, 1865. 
