A Manual of Elementary Geology / or, The Ancient Changes of the Earth and its Inhabitants as Illustrated by Geological Monuments

by Sir Charles Lyell

Fig. 271.

Caryophyllia annularis, Parkin. Coral rag, Steeple Ashton.

Fig 272.

Astrea. Coral rag.

One of the limestones of the Jura, referred to the age of the English coral rag, has been called "Nerinæan limestone" (Calcaire à Nérinées) by M. Thirria; Nerinæa being an extinct genus of univalve shells, much resembling the Cerithium in external form. The annexed section ([fig. 273.]) shows the curious form of the hollow part of each whorl, and also the perforation which passes up the middle of the columella. N. Goodhallii ([fig. 274.]) is another English species of the same genus, from a formation which seems to form a passage from the Kimmeridge clay to the coral rag.[261-A]

Fig. 273.