



The li' primitive types ^ho\\. in their earliest ipeoie*, the 



contrast Mini plent itude of 1 hei r cha nic; 



This plent itnde Mini tliis coiitrM>1 M IT :i box e .-ill rem:irkab|e 

 in two slr:iir|n t \ pes : ( hi In ><-er:is Mini l:it hnioi-rr.-is One 

 Also in some species tin- in:i\iimim of >i/e known. Bfl in 

 \niif. ferOX Hill, of ('MIIM<IM. The plentitiide oftypicMl Hiar- 

 acters and the si/.e not surpassed by Inter M | |>eM ri n- Species, 

 Mre in di-M<-eordMiiee with ihc slow Mild BUOCGBSive pFOj 

 Mtt rihnted to evolut ion. 



Tin- I '1 primitive t \ pes Mre very uii(Mjii:illv dist rilmled in the 

 p:il;iM)/ic countries. This distribution indicMtes no eeiitie 

 of ditl'tision. no point of depMrtuiv tor evolution. 

 Anionir the 1-J jiriinitivf tyjirs. :in- lonnd those the mo-t con- 

 trasted in form Mild structure. Kx. : 



OrthocerMs. with st r.-MLi'lit shell. 



CyrtocerMs. with curved shell. 



\Miitilus, comph'tely spirul in the SMIIIC plMiic. 



Trochocei-Ms. douhly spiral. 



r>MthmocerMs. shell straight, but characterized by MU obso- 

 lett i siphon. 



In order to derive from a common ancestor types so much 

 ditferentiMtcd. one must IIMVC MH indefinite number of ucnera- 

 tions and of t ransit ion-forms, of which there remain no trace 

 whatever. 



The 1 t types posterior to the 1 > primitive types, also appeared 

 as suddenly, without beiiiii announced by any transit ion-form. 

 MS for example: Ascot-mis and Goniatites. One can :ipply 

 to them also tin- preceding observation. 



Tin- vertical position of the ill tyjtes in respect to their lirst 

 a|)peMi-Miice. oll'ers M com bi iiM t ion the most opposed to evolu- 

 tion, for insteMd of showing a successive progress in the 

 number of lirst. appearances, it presents a rapid diminution 

 thereof. In fact : 



1C of these -Ji; first :ipp(':ir.-ni<-i's (comprising the 1J primi- 

 tive types) ;uv found irithin the limits of the 2d I'MUIIM. 

 s in the limits of the :;d I'MUIIM. 

 1 tow-mis the end of the Ih'voniMii fauna. 

 1 during the Koceiie period. 



