362 M. E. Favre on some Works relating to 



XLII. — On some Worhs relating to a new Classification of 

 Ammonites. By Eenest Favee*. 



The abundance with which Ammonites are distributed in the 

 deposits of the secondary epoch, the variety and beauty of these 

 fossils, and their importance in the classification of strata have 

 long attracted the attention of naturalists. When the known 

 species of this group increased in number, and a greater diver- 

 sity of forms was discovered, the necessity of introducing some 

 subdivisions among them came to be felt. Nevertheless, as 

 no representative of this genus has yet been found living, and 

 the organization of the animal was and still is in great part 

 unknown, the various classifications proposed were only based 

 on the most apparent characters of the shell — that is to say, on 

 its general form, the nature of its ornaments, and that of the 

 septa. • Thus it was that the Ammonites were divided into 

 various families, the Heteropliylli^ Glohosi^ Ornati^ Cristatiy 

 &c. 



The great works of M. Barrande on the Cephalopoda of the 

 Silurian strata, the development of palseontological collections, 

 and a very complete study of the anatomy of the Nautilus (the 

 only tetrabranch now living) have thrown, within the last 

 few years, a new light on the organization of the Ammonites. 

 Important characters have been recognized, and have served 

 as a basis for a classification into various groups which have 

 been called genera. In this way a number of new names, such 

 as Arcestes, Phylloceras^ Perisphinctes^ &c., of which the use 

 has not yet spread beyond a certain number of paleontologists, 

 have been introduced into certain works published in Germany. 

 The new classification f, however, is not complete ; and it re- 

 lates especially to the Ammonites of the Jurassic formation, of 

 which the museums of Munich and Vienna possess admirable 

 collections. Moreover the naturalists who have created and 

 adopted it still retain the old designation for the Ammonites 

 from this formation which are not yet classed, as well as for 

 tlie greater part of the Cretaceous Ammonites, until new mate- 

 rials enable the work to be completed. 



Professor Suess has the merit of first drawing attention to 

 the characters which may serve to establish a new classifica- 

 tion of Ammonites, and directed in a quite different course from 

 his predecessors' the researches on this group. M. Laube, ]\I. 



* Translated by W. S. Dallas, F.L.S., from the Bibliotheque Univer- 

 selle, Archives des Sciences, January 15th, 1873, pp. 1-23. 



t I shall not speak here of an attempt at classification which has been 

 made in America by Prof. Ajxassiz and Mr. Hyatt, and which rests upon 

 very dillereut principles from those of the German classification. 



