Vol. 58.] JURASSIC OF THE SOUTH WALES DIRECT LINE. 723 
beds thus concealed may, with practical certainty, be assigned to 
the zone of Ammonites Bucklandi. 
That Gryphcea arcuata occurs in great abundance in these beds 
may be deduced from the numerous groups of closely-packed valves 
belonging to this species, which were to be seen outside a row of 
cottages near the new station. The fossils, we were informed, came 
from these beds. Of the truth of this assertion there is strong 
negative evidence, in the fact that we have found no such packed 
masses of the species either in the beds above or below. 
(f) The Turneri-Shales. 
The first exposure that we were able toexamine was immediately 
west of the first bridge, which lies east of the new station. Higher 
- beds were exposed to the east of the bridge in drainage-cuttings ; 
and, about 300 yards east of the bridge, a fault, with a downthrow - 
of 30 feet towards the west, enabled us to examine beds a little 
below those exposed just west of the bridge. 
Lithologically, this series of beds consists of a very uniform suc- 
cession of shales (7 or 8 feet thick) separated by thin limestone-bands 
(3 or4 inches thick). There are also several impersistent limestone- 
bands, made up of separate nodules; these nodules assume the most 
varied forms, such as ovoid, spherical, club-shaped, dumbbell-shaped, 
ete. A great number of these nodules exhibit the usual] concentric- 
shell structure, and are undoubtedly ordinary concretions. In many 
others, however, this structure is apparently absent; and since, when 
examined in situ, they are seen to have a conspicuous lamination 
parallel to that of the shales in which they lie, it is possible that such 
nodules may be those portions of an originally continuous sheet which 
have offered the greatest resistance to the solvent action of water. 
Throughout the series, the shales are perfectly fissile, and can be 
split into lamine as thin as paper. 
Paleontologically, the whole series is characterized by the 
abundance of Ammonites (Arnioceras ) semicostatus and its mutations. 
Arietites Turners is not uncommon, and there are at least two species 
belonging to the genus Coronzceras, one of which is nearly allied to 
Amm. (Coroniceras) Buckland. These ammonites occur in great 
profusion, in a crushed state, on the surfaces of the shale-lamine ; 
but they are also found in considerable numbers, either as, solid 
fragments, or firmly embedded in limestone-nodules. 
In the lowest beds of this series, single specimens of Gryphew 
arcuata are fairly plentiful, and the species occurs somewhat rarely 
near the top, where it is associated with Waldheimia (Zeilleria ) 
indentata. Belemnites acutus was found at more than one level. 
The shales crowded with crushed ammonites of the semzcostatus- 
and Purneri-types immediately call to mind the similar series at 
Lyme Regis; while the occurrence of typical Arvetites Turneri firmly 
embedded in limestone-nodules suggests the precisely similar form 
from Barrow (near Bristol). The association of Ammonites semi- 
costatus, Zeilleria indentata, Gryphea arcuata, and Belemnites acutus 
ove 
