112 



THE LIAS AMMONITES. 



cygnipes and Cardinia crassissima ; and he observes that the appearance of this beautiful 

 species has only an instant of duration in time, for in all the Basin of the Rhone it 

 occupies only a very limited vertical space, whilst the remains of AmaltJieus margaritatus 

 fills nearly all the enormous thickness of the Middle Lias. 



Table showing the extension of the Middle Lias in the British Islands, Belgium, France, 

 Switzerland, Germany, Austria, and Italy, with indications of the Liasian Ammonite- 

 zones found in some typical regions of the European area} 



Ammonite-zones 

 of the 



British Islands. 



1 



France, 

 Departments of. 



13 



a 

 .1 



Germany. 



p 



sA 



« 





























tii) 







Middle Lias. 



'ha 



a 



1 



13 



a 

 to 



.3 



i 

 i 



3 



<5 



O 



a 



J3 



i 



1 



i 



So 



> 

 W 



1 

 1 



<) 



13 



SPINATUS 



* 

 * 





* 

 * 



* 





* 

 * 







* 



* 















MAUGARITATUS 





» 



* 



* 



« 



* 





* 



* 



« 



* 



* 



HENLETI 



* 





* 







* 



$ 



* 



% 



% 



-:^ 



^ 



* 







* 



IBEX 



* 





* 



* 



« 





* 





* 



* 



* 



* 





JAMESONI 



* 

 * 



* 

 * 



* 

 « 



* 



* 







* 





* 





* 



* 









AB.MATUM 



* 





* 











* 



* 









In the above table I have separated the Armatum from the Jamesoni zone, although 

 united with it in the text, because the stratum with Aegoceras armatum forms a good 

 Ammonite-zone, although most of its other Molluscan Eauna ascend into higher beds. 

 When the Armatum-group is described and figured it will be shown that a most 

 interesting series of forms range themselves around the original Sowerbyan type, although 

 differing in many specific characters from that Ammonite ; the whole forming a remark- 

 able assemblage of the Aegoceratid^, which appeared with the dawn of the Middle 

 Lias, and had, it would seem, a very limited life in time, 



' In addition to the works already cited in the description of the diflferent zones of the Middle Lias on 

 the European Continent I have to add ' Geologie der Schweiz,' by Professor B. Studer, Zurich, 1851 ; 

 'Die Cephalopoden aus dem Lias der Nordostlicben Alpen," by Franz Ritter von Hauer, Wien, 1856; 

 'Studii geologici et paleontologici suUa Lombardia,' by Stoppani, Milan, 1857; 'Der Jura in Franken, 

 Schwaben, und der Schweiz, verglichen nach seinen palseontologischen Horizonten,' by Dr. W. Waagen, 

 Munich, 1864. 



