Catenipora escharoides.
Among the corals in which this formation is very rich, the Catenipora escharoides, Lam. ([fig. 423.]), or chain coral, may be pointed out as one very easily recognized, and widely spread in Europe, ranging through all parts of the Silurian group, from the Aymestry limestone to the bottom of the series.
Another coral, the Porites pyriformis, is also met with in profusion; a species common to the Devonian rocks.
Cystiphyllum Siluriense ([fig. 425.]) is a species peculiar to the Wenlock limestone. This new genus, the name of which is derived from κυστις, a bladder, and φυλλον, a leaf, was instituted by Mr. Lonsdale for corals of the Silurian and Devonian groups. It is composed of small bladder-like cells (see [fig. 425. b.]).
2. The Wenlock Shale, which exceeds 700 feet in thickness, contains many species of brachiopoda, such as a small variety of the Lingula Lewisii ([fig. 412.]), and the Atrypa reticularis ([fig. 414.]) before mentioned, and it will be seen that several other fossils before enumerated range into this shale.
Fig. 424.
Porites pyriformis, Ehren. Wenlock limest. and shale. Also in Aymestry limestone, and L. Ludlow.
a. Vertical section, showing transverse lamellæ.