211 
\ 
AMMONITES stellaris. 
TAB. XCIIL 
Spec. Char. Involute, rather depressed with a 
rounded sulcus on each side of an obtuse keel ; 
inner turns about two-thirds exposed ; volutions 
about four with their sides flatfish; radii nu- 
merous, straight : aperture quadrangular, with 
the interior angles rounded. 
The sinuous margin of each septum is crossed by two 
radii, the septa are placed at each fourth radius. The 
siphuncle is contained in the keel, as in most of the cari- 
nated species. The aperture is rather longer than wide; 
its length is two-fifths the diameter of the shell. Surface of 
the shell marked with obscure rather distant decussating striae. 
Found rather abundantly at Lyme in Dorsetsh 4 e; Mr. 
Strangewayes has forwarded it to me. I broke one sped* 
men to find the siphuncle, and thus separated three or four 
joints by the septa, so as to hold together like a chain, being 
moveable like the dissepiments of some other species, 
without falling apart, the sutures fitting in a sort of dovetail 
manner. This specimen is remarkable for the more central 
volutions having a pentagonal figure. When the shell 
covers the cast the sutures of course are covered, and in 
some species the external form is different from the internal, 
but a part of the shell which remains towards the front at 
the bottom shows that in this they do not probably differ. 
