134 On the Inferior Oolite and Lias of Northamptonshire, &c. 
dubius, Rostellaria (abundant), Cidaris*, Nucula, Avicula, and 
Aptychus. These are succeeded by two or three blue marly 
bands divided by shale, which contain a univalve like a Ceri- 
thium, Avicula, Nucula, Pholadomya, Pecten, Astarte, and Am- 
monites. A light blue, slightly indurated marl reposes imme- 
diately upon the Marlstone. The total thickness of these clays 
and marls forming the base of the Upper Lias is about 30 feet. 
* A similar small species of Cidaris (C. minuta) occurs abundantly with 
spines attached in the Upper Lias shale at Gretton near Winchcomb, where 
a fine specimen of a Lepidotus was lately discovered in the ‘ fish bed,’ and 
is now in the collection of my friend Dr. Wright. 
