A manual of palaeontology for the use of students : with a general introduction on the principles of palaeontology / by Henry Alleyne Nicholson and Richard Lydekker.
- Date:
- 1889
Licence: Public Domain Mark
Credit: A manual of palaeontology for the use of students : with a general introduction on the principles of palaeontology / by Henry Alleyne Nicholson and Richard Lydekker. Source: Wellcome Collection.
Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.
877/1688 page 855
![prises about three hundred species, all of which are confined to the Pateozoic rocks. The earliest types appear in the later Silurian deposits, and have very simple suture-lines. In the Devonian and Carboniferous rocks numerous forms of Goniatites are known ; and the latest representatives of the group are found in the Permo- Carboniferous beds of the Salt Range in India. In certain of the Devonian and Carboniferous Goniatites the sutures become com- plicated by the increase of the number of lobes and saddles, till a near approach is made to the structure of the septa in the Ammonites. Family 3. Arcestid^.—In this family the shell is discoidal, and the body-chamber is very long, extending over one or one and a half whorls. The surface of the shell is smooth, or may be adorned with transverse striae, ribs, or folds. The suture-lines show very numerous lobes and saddles, and both of these are laterally incised, thus becoming foliaceous (fig. 770). No Aptychusis present. [In some forms a horny Anaptychus appears to have existed.] The members of this, as of all the remaining families of the Ammonoidea, are distinguished from the ClymeniidcB and Goniati- Fig. 770.—Suture of Cyclolohus Oldhami, one of the A rcestidie. Permo-Carboniferous, I ndia. (After Waagen—copied from Zittel.) iidce by the greater complexity of their septa and the more ornate form of the sutures resulting from this; while the septal necks are always turned forwards, and the shell is thus prosiphonate. Formerly all these forms were grouped under a comparatively small number of genera, such as Ceratiies, Ammonites, Hamites, Turn- Hies, Baculites, &c., distinguished principally by the mode of growth and the resulting form of the shell. By far the most important of these groups was the comprehensive genus Ammonites, embracing the great series of forms commonly known as Ammonites. Through the researches of Hyatt, Neumayr, Mojsisovics, Waagen, von Zittel, and other well-known investigators, it has now been shown that the old genus Ammottites can no longer be maintained, but that the types formerly included under this name admit of a natural](https://iiif.wellcomecollection.org/image/b21932839_0877.jp2/full/800%2C/0/default.jpg)
