16 CLASS CEPHALOPODA. 
spiral portion whatever. Some of them are round, and others 
compressed. ‘The last sometimes have a lateral siphon. 
There are some with their first cells arched. The Ha- 
MITES, Sowerb., are arcuated. 
Finally, those which vary most from the usual form of this 
family are the TURRILITES, Montf. 118, where the whorls, so 
far from running in the same plane, suddenly descend, giving 
to the shell that form of an obelisk which is called turreted. 
It is also thought, and from similar considerations, that we 
should refer to the cephalopoda, and consider as internal 
shells the 
CAMERINES, Brug. NUMMULITES, Lam., 
Commonly called nwmmulites, lenticular stones, &c., which 
are only found among fossils, and present, externally, a lenti- 
cular figure, without any apparent opening, and a spiral cavity 
internally, divided by septa into numerous small chambers, but 
without a siphon. They are amongst the most universally 
diffused of all fossils, forming, per se, entire chains of calca- 
reous hills and immense bodies of building stone. 
The most common, and those which attain the greatest 
size, form a complete disk, and have only a single range of 
cells in each whorl. Some very small species are also found 
in certain seas. 
The margin of other small species (the SIDEROLITHES, 
Lam.), both fossil and living, are bristled with points, which 
give them a stellated appearance. 
The labours and researches, conducted with infinite patience 
by Bianchi (or Janus Plancus), Soldani, Fichtel, Moll, and 
D’Orbigny, have ascertained an astonishing number of these 
chambered shells without a siphon, like the nummulites, that 
are extremely small and frequently microscopical, both in the 
sea, among the sand, fuci, &c., and in a fossil state in the sand 
formations of various countries. 
