372 M.E. Favre on some Works relating to 



2. Integument calcareous. 

 Aptychtis Numida, Coq. Shell unknown. (Si- 



detes?) ? 



II. Gland double, with the Aptyckm calcareous. 

 1. Aptychus possessing furi'ows on tlie external side. 



Aptychus thin, presenting externally a layer of 

 conchioline, •wliich is easily detached. Cham- 

 ber short ; apertural margin falciform, with 

 an acute ventral appendage Harpoceuas, Waag. 



Aptychus thick, having internally a solid layer 

 of conchioline. Chamber short ; apertural 

 margin falciform, with a rounded ventral 

 appendage Oppelia, Waag. 



Chamber short, having near the aperture a 

 groove or a swelling ; apertural margin pro- 

 vided with lateral auricles and a rounded 

 ventral appendage Haploceras, Zitt. 



Chamber pretty long ; last turn detached from 

 the others ? Scaphites, Park. 



2. Aptychus thin, granulated externally. 



Chamber long ; apertural margin simple or 



furnished with auricles Stephanoceras, Waag. 



Chamber long ; aperture naiTowed byafm-row, 



simple or furnished with auricles Pebisphinctes, Waag. 



Chamber short; aperture simple or furnished 



with auricles Cosmoceras, Waag. 



3. Aptychus thick, smooth, and punctated externally. 



? Chamber long. Umbilicus large. Shell with 

 furrows ; apertural margin with a nasiform 

 ventral appendage Simocebas, Zitt, 



Chamber short ; apertural margin generally 

 simple Aspidoceras, Zitt. 



In this table I have employed the words ventral and dorsal 

 in place of siphonal and ayitisiphonal^ because the appendages 

 to which they apply, and which are placed at the extremity of 

 the last cliamber, are not in any way related to the siphon. 

 Two newly established genera must be added, viz. PinacoceraSj 

 Mojsis., allied to Arcestes, and Peltoceras^ Waag., intermediate 

 between Perisphinctes and Aspidoceras. 



This table is far from embracing the whole of the family of 

 Ammonitid^e. There are wanting Ceratites and Goniatites^ 

 long since separated from the true Ammonites, all the unrolled 

 Ammonitidge, already classified in accordance with other cha- 

 racters, and to which the genus ScapJiites forms the transition ; 

 and, lastly, many true Ammonites for which no genus has yet 

 been created, and to which, in the meanwhile, it is necessary 

 still to leave the old name, are necessarily omitted from it. 



As the nature of this memoir does not permit me to give 



