MODERN CLASSIFICATION. 
of the Ammonite shell/ " Die Zusaramensetzung cler spiralen Schale." The reform so well 
inaugurated by Professor Suess was ably followed up by Dr. W. Waagen/ who directed 
attention to the importance of the study of the Avtychus and Anapiychus, and the presence 
or absence of this body in the Ammonite shell. The observations made by Waagen on 
the Apfi/cJms\\e described and applied in the diagnosis of the genera proposed for several 
Jurassic species. In the following figure the Aptyclms carinatus (fig. 98) is seen apart 
from the shell. In figure 97 it is seen lying in the body-chamber of an Ammonite, 
and in figure 99 the Aptychus is vertical, as if closing the aperture of the shell. 
Fig. 97. Fig. 99. 
The following organic features are considered as elements of primary importance in 
studying the Ammonite shell, and their combination constitutes characters for the 
diagnosis of the generic groups. 
Firstly. — The structure of the lobes and their suture-line have been fully studied by 
Fig. 100. — Disposition of the lobes Fig. 101. — Disposition of tlie lobes Fig. 102. — Disposition of the Iol)es 
(d, l, l', a) in Amal. margari- (d, l, l', a) in Phylloceras hetero- (d, l, l', a) in Phyll. heterophyl- 
tatus, Montf. phyllum. lum, Sow. 
^ 'Ueber Ammoniten,' 2 Abth., Sitzungsber. der Mathemat. Classe der Wiener Akademie Bund 
61, Abth. 1, 1870. 
2 "Die Formenreibe des Ammonites subradiatns," Benecke's ' Geogn.-Palseont. Beitrage,' Bd. ii, 186i). 
