105 
AMMONITES Jamesoni. 
TAB. DLV.—jig. 1. 
Spec. Cuar. Discoid, radiated ; sides flattened ; 
volutions 5 or 6; the inner ones exposed ; 
radii large, simple, obtuse, equal to the spaces 
between them, bent towards the aperture as 
they pass over the front. 
Tue numerous large radii, considerably bent as they 
pass over the front, strongly characterize this shell ; the 
aperture is nearly twice as long as wide. 
Collected on the Isle of Mull, by R. I. Murchison, 
Ksq., during a tour which has been the foundation of a 
valuable paper lately read before the Geological Society. 
At the request of this gentleman I am happy to com- 
memorate the celebrated Geologist whose name it bears, 
and who needs no panegyric from me. It has also been 
found in Robin Hood’s Bay. 
nia 
AMMONITES navicularis. 
TAB. DLV.—fig. 2. 
Spec. Cuar. Umbilicated, costated ; coste large, 
numerous, annular, simple ; whorls ventricose, 
very few ; the inner ones half exposed ; aper- 
ture transversely oblong. 
Syn. Ammonites navicularis. Mantell, Geol. of 
Sussex, 198. ¢. 22. f. 5. 
Asout three whorls, rapidly increasing, compose this 
Ammonite: all the cost reach the edge of the umbilicus, 
half or more of them turn into it, and at the same time 
are rather enlarged ; the coste and the spaces between 
them are nearly equal. 
From the lower Chalk at Guildford: presented to 
Mrs. Murchison by Mr. Mantell. It is only half the size 
of the one figured in the Geology of Sussex, where it is 
spoken of as a very rare shell. 
