DISTRIBUTION OF THE MOLLUSCA IN TIME. 219 



I. Generic Types. 



1. Absence of cephalopods in the primordial silurian fauna of 

 all the countries where it has been ascertained to exist ; that 

 is to say in about 25 natural basins, largely spread OA'er the 

 two continents. This absence is in harmon}^ with that of the 

 acephala and the rarity of gasteropoda and heteropoda in 

 the same fauna. It is inexplicable by the theories of evolution. 



2. Sudden appearance of 12 types of cephalopods in the first 

 aspect of the second Silurian fauna. 



This sudden appearance is as inexplicable as their total 

 absence in the primordial fauna. This number, 12, consti- 

 tutes nearl}^ half of the 26 types admitted in his studies, 

 among the 3 families : Nautilidse, Ascoceratidse and Gonia- 

 tidse. 



3. The 12 primitive types show, in their earliest species, the 

 contrast and plenitude of their characters. 



This plenitude and this contrast are above all remarkable 

 in two straight types : Orthoceras and Bathmoceras. One 

 sees also in some species the maximum of the size known, as 

 in Naut. /eroic Bill, of Canada. The plenitude of typical 

 characters and the size not surpassed by later appearing 

 species, are in disaccordance with the slow and successive 

 progress attributed to evolution. 



4. The 12 primitive types are very unequall}^ distributed in the 

 palaeozoic countries. This distribution indicates no centre 

 of diffusion, no point of departure for evolution. 



5. Among the 12 primitive types, are found those the most 

 contrasted in form and structure. Ex. : 



Orthoceras, with straight shell. 



Cyrtoceras, with curved shell. 



Nautilus, completely spiral in the same plane. 



Trochoceras, doubly spiral. 



Bathmoceras, shell straight, but characterized by an obso- 

 lete siphon. 



In order to derive from a common ancestor types so much 

 differentiated, one must have an indefinite number of genera- 

 tions and of transition-forms, of which there remain no trace 

 whatever. 



6. The 14 types posterior to the 12 primitive types, also appeared 

 as suddenly, without being announced by any transition- 

 form, as for example : Ascoceras and Goniatites. One can 

 apply to them also the preceding observation. 



*I. The vertical position of the 26 types in respect to their first 

 appearance, offers a combination the most opposed to 

 evolution, for instead of showing a successive progress in the 

 number of first appearances, it presents a rapid diminution 

 thereof. In fact : 



