18 
external marks, but the present species is sufficiently pre- 
served to show if there had been any. The upper shell 
has a little remains of the shining outside, the upper part 
is a little broken, the lower part or beak is very entire, 
and shows some of the teeth; it is filled with hardish 
marle, so as to hide the remainder of the teeth, which, 
however, are seen in the right hand figure of a smaller 
shell, which is finely preserved with the polished coat 
and a brown stain of [ron Pyrites, the beak is enveloped 
in Pyrites. The left hand figure is the dorsal view of the 
same shell. ‘The lower figure is more injured, showing 
by the breaks in two or three places the dark Pyrites which 
fills the shells, and adheres over the cracks. I am obliged 
to the generous Mr. Weatherell, who discovered this shell 
at Highgate, for the specimens figured. 
It is to be observed that accidentally the plate of these - 
shells has been reversed in the engraving, bringing the 
mouths to the left instead of the right side. 
