a neiv Classification of Ammonites. 363 



Zittel, and M. Waagen afterwards, especially occupied them- 

 selves with tliis question*. The classification proposed by M. 

 Suess rests in j5;reat part on the size of the last chamber and 

 on the nature of the appendages to the mouth of the shell, 

 which he believes to be in relation with the essential characters 

 of the animal. That of M. Waagen, whilst taking into ac- 

 count these characters, is based on the nature of the Aptychus^ 

 Avdiich plays, as I shall show, an essential part in the organi- 

 zation of the Ammonite. 



The last cJiamber^ the size of which is constant in each group 

 of Ammonites, differs much from one group to another. In 

 some of them it occupies as much as one turn and a half, in 

 others hardly half a turn. This difference is often connected, 

 according to M. Suess, with differences in the form of the 

 margin of the aperture, and in important anatomical characters. 

 According to this learned paleontologist, in the Ammonites 

 furnished with a large chamber the adductor muscles wei-e 

 probably placed on tlie sides near the margin of the shell, 

 which generally presents the form of a crescent. In the much 

 more numerous Ammonites which have a shorter chamber the 

 latter encloses only a part of the animal ; the margin of the 

 aperture is then furnished with appendages of various forms, 

 sometimes simple and discoidal [myotheque], sometimes more 

 elongated and presenting a myotheca united to the shell by 

 a longer or a shorter peduncle {inyolahe). As these names in- 

 dicate, these appendages served, in the opinion of M. Suess, 

 as points of attachment for the muscles. 



M. Waagen has opposed this opinion. The muscles have, 

 according to him, a part too important in the organization of 

 tlie Ammonite, and the life of tlie animal depends too much 

 upon their preservation, for them to be thus placed on the edge 



* The following are the titles of the various works in which this sub- 

 ject is treated : — . 



1805 and 1870. Ed, Suess, "Ueber Ammoniten," Sitzungsber. k. Akad. 

 Wiss. Wien, lii., Ixi. 



18<)8. Zittel, Palfiontologische Mittheilungen. Die Cephalopoden der 

 Stramberger Schichten. 



18(39. Laube, " Ueber Ammonites Aon uud seine Verwandten," Sitz- 

 ungsber. k. Akad. Wiss. Wien, lix. 15. 



1800. Waagen, " Die Formenreihe des Ammonites suhradiatus,^'' in Be- 

 neke's Geogn.-pal. Beitr. 1809, ii. 183. 



1870. Zittel, raliumtologisclie Mittheilungen. Die Fauna der siltern 

 Cephalopoden-fiihrenden Tit lionbildungeu. 



1870. Waagen, " Ueber die Ansatz.stollen der Haftmuskeln beim Nau- 

 tilus und den Animouitideu," Palieoutographica, herausg. v. Dunker und 

 Zittel, xvii. 185. 



1871. Waagen, " Abstract of results of examination of the Ammonite- 

 fauna of Kutch, &c.," Records of the Geol. Surv. of India, 1871. 



