2. AM. BRODIEI. OOLITE.
3. AM. HUMPHRIESIANUS. LIAS.
4. AM. WALCOTTI. LIAS.
In general outline it will be seen that the ammonite somewhat resembles the nautilus, and yet there are characteristic differences that are so striking as to mock the development hypothesis. In the first place, the shell of the ammonite, though of the same flat discoidal form as that of the nautilus, appears to have been much thinner; secondly, it will be seen that the whorls of the ammonite are rounder and more in number than those of the nautilus; and lastly, the siphuncle, of which more presently, runs round the chambers of the ammonite, but through the chambers of the nautilus. Let us look a little at each of these peculiarities; and to aid us, we give below two drawings of sections of ammonites, and two drawings of a nautilus.
AM. KŒNIGI LIAS.
