164 
THE AVONIAN OF THE AVON GOROE 
The reference to Eumetria rests upon the striking similarity 
of the external characters, as shown in the following hst of 
properties common to our species and to the type figures of 
Eumetria : — 
Elongate oval form. 
Absence of fold or sinus, and uniplanar valve-intersection. 
Simple low radial ribs, all of the same pattern. 
Small ears to the brachial valve, giving it a Pec^eti-like 
appearance. 
In the pedicle valve, a tall area formed laterally of two 
concave narrow strips which are marked ofi from the 
rest of the valve by sharp ridges ; triangular delthyrium. 
Shell structure strongly punctate. 
The Rhynchonellids. 
Camarotcechia. 
Camarotcechia 7nitcheldeanensis. 
Hinge plates of Brachial valve. 
Here are included small ‘ Rhynchonellas ’ in which : — 
The ribs are sharp and continuous from back to margin. 
Fold and sinus are well developed. 
The beak is small and pointed. 
The genus is however based entirely upon internal characters : — 
In the brachial valve, the ‘ hinge-plate ’ (from which the 
crurse project) is formed of two plates closely approxi- 
mated in the middle line ; each separate plate is sup- 
ported, underneath, by one of the sheets of the spondylium 
into which the mesial septum splits. 
