9 
AMMONITES angulatus. 
TAB. CVII— Fig. I. 
Spec. Chars Involute; volutions six or more., 
exposed, angular at the back within ; radii 
prominent, split over the front, commencing 
in the cast from a narrow concave space. 
The aperture is rather longer than wide, its width equal s 
one-fifth the diameter of the shell; around the concentric 
angle at the inner part of the whorl is a narrow concave 
space, from the outer part of which commence the radii : 
this angle and the concave space are indistinct on the out- 
side of the shell. 
I received this, I think, rare and curious specimen from 
the Whitby Alum Clay, by favour of Mr. J. M. Sowerby, 
among various other specimens. The line at the inner 
part is apparently only in the cast, the small shelly part 
remaining on the specimen being destitute of it. The shell 
appears to be replaced by a mixture of pyrites, Carbonate 
of Iron, and Limey marie, but more stony within. The 
sinuated margins of the septa are rather close, but not par- 
ticular or very distinct; if any thing they are more acute 
than in the A. communis. I have not seen the siphuncle 
or plains of the septa, but I presume they bear a close 
resemblance to the following. Indeed the resemblance 
between this species and communis is so general, that if 
the internal angle were not observed, it would, from its 
external appearance, be considered as the same, yet I 
expect it is always more ovate in the opening, with an 
approach to a flattish front. The shell seems somewhat 
laminated. The forked divisions in the front of the shell 
turn upwards in both * 
