258 THE TRANSFORMATIONS OF THE ANIMAL WORLD 



in the adult state, in a very small number of genera 

 of the Devonian epoch (Gyrtoclymenia, Mimoceras) ; 

 in the other saddleless genera of the Primary epoch 

 it is limited to the first partition. In a second type, 

 the broad-saddled type of Branco, the first suture 

 is characterized by a large convex sinus forward, or 

 ventral saddle. This type is only observed in 

 the Ammonoids of the Primary epoch, and in 

 a few families of the Triassic. In all other Am- 

 monites, Triassic, Jurassic, and Cretacean, the 

 first suture denotes the third or narrow-saddled 

 type, characterized by a long and narrow central 

 saddle. There is then in the form of the first 

 suture of the Ammonians a progression from the 

 saddleless type to the narrow-saddled, with em- 

 bryogenic accelerations (tachy genesis), that is to 

 say, suppression first of the saddleless stage, and 

 then of the broad-saddled one, as we rise in the 

 series of ages. 



If, starting from the first saddleless, broad- 

 saddled, or narrow-saddled type, all of which are 

 very simple, we study the successive sutures of 

 the same species of Ammonite, these partitions are 

 observed to become gradually more complicated ; 

 the median or ventral saddle first becomes hollowed 

 out in the middle with a sinus or ventral lobe, at 

 the bottom of which there frequently appears a 

 projection or secondary ventral saddle. At the 

 same time one sees produced, on the sides of the 

 suture line, saddles and lateral and more and more 

 complex lobes and accessories. Beginning at the 

 third suture, in all Ammonoids there occurs the 

 Goniatite stage, characterized by several simply 





