230 
THE LTAS AMMONITES. 
The difficulty of finding the Aptychis in situ in the shells to which it belongs will 
long render this important anatomical character of little practical value as a factor in the 
diagnosis of the different groups, and for this reason it has not been employed by 
Dr. E. Mojsisovics or by Professor Neumayr in the classifications given by them. 
The following classification of the new Ammonite genera was proposed by Dr. 
Waagen/ and a like grouping has since been pubhshed by M. E. Eavre.^ 
Genera of Ammonites, 
A. Aptyclms absent. 
Body-chamber short ; appendage ventral, Phylloceras, Siiess. 
Triassic and Cretaceous. 
Body-chamber short, appendage dorsal. Lytoceras^ Suess. 
Trias. Juras. Cretaceous. 
Body -chamber very long, one and a half to two whorls, Arcestes, Suess. 
mouth border dissimilar. Triassic. 
Body-chamber short, mouth-border falciform, appen- Trachyceras, Lauhe. 
dage ventral, sculpture Argonautiform. Triassic. 
B. Aptychus present. 
I. Aptyclms undivided. • 
1. Horny {AnaptycJius) — 
Body-chamber long, one to one and a half whorls, Arietites, Waagen. 
mouth-border with pointed ventral appendage. Triassic and Liassic. 
Body-chamber from two thirds to an entire whorl, Aegoceras, Waagen. 
mouth-border with rounded ventral appendage. Triassic and Liassic. 
Body-chamber short, one half to two thirds of a Amaltheus, Montfort. 
whorl, mouth-border with long ventral appendage. Trias., Juras., Cretaceous. 
2. Calcareous, — Aptychus Numida, Coquaud, 
Shell unknown {Sidetes ?) Cretaceous, 
* ' Ueber die Ansatzstelle der Haftmuskeln beim Nautilus uud den Ammoniden, Palseoutographica,' 
Band xvii, 5, p. 197, 1867—1870. 
2 " Sur la Classification des Ammonites," M. E. Favre, 'Bulletin de Soc. Geol. de France,' 3e serie, 
torn, i, p. 353, 1873, 
