OF BALA, CORWEN, AND GLYN CEIRIOG. 123 
TERMS USED IN THE LIST. 
‘Very rare,” when only one or two specimens of the species 
have been found. 
“Rare,” when two or three have been found. 
“‘ Frequent,” when several have been found. 
** Scarce,” when occurring here and there at long intervals. 
**Common,” and ‘“ Very common,” when plentiful and general. 
NOTES. 
Orthisina ascendens. The dorsal valve of this interesting fossil 
is but imperfectly known to paleontologists. Mr. Davipson, 
in his Silurian Brachiopoda,* figures only the ventral valve, and 
Pror. McCoy says of it—“I have not seen the entering (dorsal) 
valve of this species, but according to DE VERNEUIL and 
PANDER it is about half the depth of the receiving (ventral) 
valve.” — 
I have been fortunate enough to get together a fine series of 
this valve from the hills south of Corwen, and above the 
village of Cynwyd, The series includes casts both of the 
interior and exterior shells of both valves. I have also examples 
of both valves attached. In the interior of one specimen is 
seen the spiral coils common to the Brachiopoda. The speci- 
mens I have put down as a variety of Orthistna differ essentially 
from it in the sculpturing on the exterior surface, which is 
similar to Strophomena corrugatella, figured in Davipson’s 
Silurian Brachiopoda, Plate 41, figs. 11 and 12. There is a 
doubtful specimen of the dorsal valve in the Museum of 
Practical Geology in Jermyn Street. 
Agelacrinus Buchianus (Forbes), Protaster Saltert (Forbes), 
and one or two other species seen in other collections from this 
neighbourhood, have been found in zones 8 and 9. 
The list of fossils found in the Caradoc beds of North Wales, 
given in the third volume of the Memoirs of the Geological 
Survey, needs correction in some of its details. Several of the 
species given in the list are very doubtful, especially the 
Graptolites, said to have been found in localities doubtfully 
referred to Bala beds. Mr. SALTER, in the same memoir, says § 
that Grap/olites are absent in the Bala beds, while in the 
Cambridge Catalogue of Fossils, Grapéolithus priodon and 
Grap. sp. are given as Middle Bala species (Caradoc beds) from 
North Wales, but Peniarth ucha, N.W. of Pen-y-glog at Corwen, 
the locality given for this fossil, is suspiciously near to the slate 
*Palzontographical Memoir, Vol. vii., Plate 49, No. 4. 
+ Sedgwick and McCoy, Br. Pal. Foss., p. 231. 
Geological Memoir, North Wales, p. 272. 
