It is a curious fact, that contrivances, similar to those which existed in some of the most early forms of Ammonite, should have been again adopted in some of the most recent species of fossil Nautili, in order to afford similar compensation for weakness that would otherwise have been produced by aberrations from the normal structure of the genus Nautilus. All this seems inexplicable on any theory which would exclude the interference of controlling Intelligence.
SECTION VI.
CHAMBERED SHELLS ALLIED TO NAUTILUS AND AMMONITES.
We have reason to infer, from the fact of the recent N. Pompilius being an external shell, that all fossil shells of the great and ancient family of Nautili, and of the still more numerous family of Ammonites, were also external shells, inclosing in their outer chamber the body of a Cephalopod. We further learn, from Peron's discovery of the shell of a Spirula partially enclosed within the body of a Sepia
[1] (see Pl. 44, Fig. 1, 2,) that many of those genera of fossil chambered shells, which, like the Spirula, do not terminate externally in a wide chamber, were probably internal, or partially enclosed shells, serving the office of a float, constructed on the same principles as the float of the Spirula. In the class of fossil ash ells thus illustrated by the discovery of the animal in closing the Spirula, we may include the following extinct families, occurring in various positions from the earliest Transition strata to the most recent Secondary formations:
- ↑ The uncertainty which has arisen respecting the animal which constructs the Spirula, from the circumstance of the specimen discovered by
in which the fringed edge is partially introduced, on the descending or inward portions only, of the lobated edge of the transverse plates.
