92 
apparently continues to the very tooth of the hinge, 
upon which the lines of growth are strongly marked, 
continuing from the edge of the valve. The depth of 
one valve is equal to its smallest diameter, and this is 
about half the measure from the point of the anterior 
lobe to the beak : the cordiform pit is wider than long. 
When placed upon the prominent parts of the anterior 
lobe, the front is so obtuse, that it resembles in its 
general form a horse’s hoof ; whence the name of the 
genus. 
Found at Toddenham, near Shipston-on- Stour, in 
Gloucestershire, by the Rev. W. D. Conybeare. (See 
the upper figure.) It is also found at Fenny Compton 
tunnel, on the Oxford canal, whence the lower figure ; 
and at Cheltenham ; in all these places in the upper 
beds of the Lyas, as I am informed by Mr. Conybeare. 
