CLASSIFICATION. 11 



various systems of classification proposed by Hyatt, Neumayr, Waagen, Favre, and 

 others, he gives us that system which he himself thought it best to adopt. It is 

 quite unnecessary for me to go over all this ground again. The general principle 

 and the general mode of subdivision are now almost unanimously agreed upon and 

 recognised. I intend to introduce new genera and to restrict many of those now 

 in use; and I shall as occasion requires give my views concerning them. During 

 the last few years the introduction of new genera, to partially take the place of the 

 large subdivisions that one finds, for instance, in Dr. Wright's Monograph, has been 

 frequent. Thus, part of what Dr. Wright included under Harpoceras is now put 

 into Hammatoceras, and this genus again has been lately divided into that and 

 Sonninia. These new genera arise out of the necessities of the case. It having 

 been once agreed that a division of " Ammonites " was necessary, limits cannot 

 directly be set to such division. The introduction of Arietites, Harpoceras, and 

 Stephanoceras was a step in advance, but each included very diverse forms. 



It will thus be seen that there has been a constant tendency to more and more 

 subdivision, and I venture to advance still farther in this direction. Exception 

 may probably be taken by some persons to the number of genera into which I shall 

 propose to divide the Ammonites in this Monograph, but I would draw attention to 

 other sciences, entomology, botany, &c, and would point out the large number 

 of genera which they contain, and ask why we should not in palaeontology 

 proceed on the same lines, viz. make a genus for the reception of a group of a 

 larger or smaller number of species having certain points and characters in common, 

 distinguishing them from other groups. This will be more clearly brought out 

 in the definition of each genus, which I shall give. It is now several years since 

 Hyatt attempted to divide the Ammonites into what may be called small genera. 

 His system was at the time too great a stride in advance, and also too faulty, to 

 find acceptance. Since then we have had the division of Ammonites into genera 

 brought into ordinary use, but the genera used were much more comprehensive 

 than Hyatt's, including, in fact, not only several of his genera, but two or three 

 or more of his families in one. Now, however, we are returning towards the 

 direction taken by Hyatt, and in fact we use, on account of their priority, a number 

 of the generic names that he proposed. 



I have found that the importance of accurate examination of the various 

 suture lines was not to be overlooked, and that instead of the sutures varying 

 in specimens of the same species, as had been asserted, they were generally very 

 constant in form, not only in a species, but for a genus. I found, however, that 

 owing to the usually very perfect preservation of the Inferior Oolite Ammonites 

 in the South of England, and to collectors rejecting specimens not having the test, 

 I had often great difficulty in making out the suture line as I could wish. 



It is very singular that, so far as I know, no Aptychus has been found in the 



