156 
SILURIA. 
[Chap. VIII. 
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Certain fine, micaceous, dark-grey, shelly sandstones, in the Mulloch 
Hill on the right bank, and in the Saugh Hill on the left bank of the 
Girvan Water, contain among other fossils the following species : — 
Pentamerus oblongus; a variety of Atrypa hemisphserica ; Orthis reversa; 
0. biforata ; 0. elegantula ; Rhynchonella angustifrons ; Strophoinena pecten ; 
Bellerophon dilatatus; Murchisonia 
cancellatula, a beautiful fossil ; M. 
simplex, a Welsh species; Trochus 
Moorei; together with the well- 
Dularg. — ^gjfj, ~ known Silurian Corals Heliolites 
interstinctus and H. tubulatus, Pe- 
Rimch.TE -— A c2 traia subduplicata, Favosites alveo- 
laris, Ptilodictya (Stictopora, Hall) 
acuta, or Pt. costellata. 
Most of these species occur in 
the Llandovery rocks, and parti- 
cularly Pentamerus oblongus and 
Atrypa hemisphserica, which are 
the most abundant of the shells. 
There is also Ehynchonella (or He- 
mithyris) angustifrons of M'Coy, 
a species before mentioned (p. 88) 
as occurring in the Lower Llan- 
dovery rocks of Wales. Again, 
among the Trilobites, we have here 
Lichas laxatus, common in the 
limestone at Bala in North Wales, 
and, in the very same matrix, 
Calymene Blumenbachii. Now, 
although the last-mentioned Crus- 
tacean has been found throughout 
nearly the whole system else- 
where, it is by far more common 
in the Upper than in the Lower 
Silurian. Besides, it is here asso- 
ciated with Phacops Stokesi and 
Encrinurus punctatus, both of 
them fossils of the Llandovery 
rocks, and abundant in the Wen- 
lock formation. The shales of Pen- 
whapple Glen contain a large Or- 
thoceras, which Professor M'Coy 
has designated 0. politum, asso- 
ciated with Lower Silurian Grap- 
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