. The ancient life-history of the earth; a comprehensive outline of the principles and leading facts of palaeontological science. Paleontology. THE CRETACEOUS PERIOD. 2/3 and BacuUtes. In the genus Crioceras (fig. 204, d), the shell consists of an open spiral, the volutions of which are not in. Fig. ?201.—Aficyloceras Matheronianus. Gault. contact, thus resembling a partially-unrolled Ainmonite or the inner portion of an Ancylocei-as. In Turrilites (fig. 203), the shell is precisely like that of the Ammonite in its structure; but instead of forming a flat spiral, it is coiled into an ele- vate
. The ancient life-history of the earth; a comprehensive outline of the principles and leading facts of palaeontological science. Paleontology. THE CRETACEOUS PERIOD. 2/3 and BacuUtes. In the genus Crioceras (fig. 204, d), the shell consists of an open spiral, the volutions of which are not in. Fig. ?201.—Aficyloceras Matheronianus. Gault. contact, thus resembling a partially-unrolled Ainmonite or the inner portion of an Ancylocei-as. In Turrilites (fig. 203), the shell is precisely like that of the Ammonite in its structure; but instead of forming a flat spiral, it is coiled into an ele- vated turreted shell, the whorls of which are in contact with one another. In the gtrms Scaphites {f\g. 204,^), the shell resembles that of Ancyhceras in consisting of a series of volu- tions coiled into a flat spiral, the last being detached from the others, produced, and ultimately bent back in the form of a crosier; but the whorls of the enrolled part of the shell are in contact, instead of being separate as in the latten In the genus Hamites (fig. 204,/), the shell is an extremely elongated cone, which is bent upon itself more than once, in a hook-like manner, all the volutions being separate. The genus Ptycho- ceras (fig. 204, a) is very like Hamites, except that the shell is only bent once; and the two portions thus bent are in contact with one another. Lastly, in the genus Baadites (fig. 204, b and c) the shell is simply a straight elongated cone, not bent in any way, but possessing the folded septa which characterise the whole Ammonite family. The Baculite is the simplest of all the forms of the Ammonitidce; and all the other forms, how- ever complex, may be regarded as being simply produced by the bending or folding of such a conical septate shell in difl"er- ent ways. The Baculite, therefore, corresponds, in the series of the Ammo7iitidcB, to the Orthoceras in the series of the Nau- tilidcB. All the above-mentioned genera are characteristically, or exclusively, Cre
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Keywords: ., bookcentur, bookdecade1870, booksubjectpaleontology, bookyear1876
