a new Classification of Ammonites. 363 



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

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

 Suess rests in great 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^ 

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

 zation of the Ammonite. 



The last chamber, 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 

 otliers 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 palaeontologist, in the Ammonites 

 furnished with a large chamber the adductor muscles were 

 probably placed on the 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 [myolahe). 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 

 the Ammonite, and the life of the 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 : — 



18G5 and 1870. Ed. Suess, ''Ueber Ammoniten," Sitzungsber. k. Akad. 

 Wiss. Wien, Hi., Ixi. 



1808. Zittel, Paljiontologisehe Mittheilungeu. Die Cephalopoden der 

 Stramberger Schichten. 



18G9. Laube, " Uebcr Ammonites Am und seine Verwandten," Sitz- 

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



18(59. Waagen, " Die P\irinenn'ihe des Ammonites suhntdiatus,'' in Be- 

 neke's Geogn.-pal. Beitr. 18()!), ii. ls.'{. 



1870. Zittel, Paliiontologische Mittheilungen, Die Fauna der iiltern 

 Cephalopoden-fiihreiideii Tithonbildungen. 



1870. Waagen, " Ueber die Ansatzstellon der Haftmuskeln beini Nau- 

 tilus und den Ammonitiden," Palaeoutographica, herausg. v. Duukor und 

 Zittel, xvii. 185. 



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

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



