PLATE 7. 
2. The same specimen in a different position, showing 
the back. 
Co?Jch. IT. Catillus has been mistaken for an Ammonite; 
but It is entirely destitute of the chambered structure, which 
characterises that kind of fossil shell. 
FIG. 3 , 4 , 5 . 
CONCHYLIOLlTHUS lai awi-lites ( spharicus ) glob- 
osus umbilicatus, ambitu integro, apertura coarctata, 
disseplmentls dentato-slnuatis. S. p. 
Petrified shell — Original a Nautilus — Involute, globular, 
umbilicate. Navel deep and circular. Ambit entire, con- 
vex. The aperture, or mouth of the shell, narrow, 
contracted. Dissepiments dentato-sinuated. The siphun- 
culus, or pipe of communication, placed beneath, close on 
the back of the succeeding whirl. Its structure compli- 
cated — In each dissepiment two small lateral hollows or 
cavities, in form similar to the siphunculus, with which 
they seem to have been connected. 
This elegant fossil is not uncommon in limestone, but 
rarely occurs in as perfect a state as the specimen repre- 
sented by our drawing. In general, the dentated sutures, 
which externally mark the several dissepiments, are faint 
