74 
AMMONITES omphaloides. 
TAB. CCXLII.— Fig. 5. 
Spec. Car. Gibbose, radiated: inner whorles 
half concealed ; radii prominent, waved, bent 
forward in the middle of the front, generally 
furcated ; front broad, rounded ; mouth trans- 
versely oblong. 
Tae whorles of this shell increase so rapidly as to form 
a large umbilicus; in this respect and their gibbosity it 
differs from the preceding species ; but the form of the 
radii is very analagous: the short radii are not always 
joined to the longer ones, but when they are they fre- 
quently unite to two alternate ones on the opposite sides 
of the whorles, forming a zigzag line upon the front, as 
is shewn in the outtine. 
The shells figured upon this plate are all from the 
clay which occurs in Portland Island and near Wey- 
mouth : the first species is very abundant ; the two others 
are less frequent: they are all cast in Iron Pyrites, and 
were probably pearly shells, although now the shelly 
matter is nearly all lost. Such specimens as have been 
long exposed to the weather have lost their sulphur, but 
still retain their form. The first I have received from 
Dr. Leach and A. B. Lambert, Esq. The two latter 
along with a series of the first were transmitted to me by 
Prof. Buckland, for the purpose of being figured. 
