230 



THE LIAS AMMONITES. 



The difficulty of finding the Aptyclius 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 diff'erent 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. "W^ 

 Waagen,^ and a like grouping has since been pubhshed by M. E. Pavre.^ 



Geneea Of Ammonites. 



A. AptychuB ABSENT. 



Body-chamber short ; appendage ventral. Phtlloceras, Suess. 



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, Laube. 

 dage ventral, sculpture Argonautiform. Triassic. 



B. Aptychus present. 



I. AptycJius undivided. 



2 



Horny {Anaptychus) — 



Body-chamber long, one to one and a half whorls, 

 mouth-border with pohited ventral appendage. 



Body-chamber from two thirds to an entire whorl, 

 mouth-border with rounded ventral appendage. 



Body-chamber short, one half to two thirds of a 

 whorl, mouth-border with long ventral appendage. 

 Calcareous, — Aptyclms Numida, Coquand. 

 Shell unknown {Sidetes?) Cretaceous. 



Arietites, Waagen. 



Triassic and Liassic. 

 Aegoceras, Waagen. 



Triassic and Liassic. 

 Amalthetjs, Mont/ort. 



Trias., Juras., Cretaceous. 



1 • Ueber die Ansatzstelle der Haftmuskeln beim Nautilus und den Ammoiiiden, Palseontograpliica,' 

 Band xvii, 5, p. 197, 1867—1870. 



2 " Sur la Classification des Ammonites," M. E. Favre, 'Bulletin de See. G^ol. de France,' 3e serie, 



torn, i, p. 353, 1873. 



