312 OUR COMMON BRITISH FOSSILS. 



fossil, Goniatites Listeri, as large as the palm of one's 

 hand, and frequently converted into iron pyrites. 



The Ceratites of the Muschelkalk (Trias) of 

 Germany is nearly allied to the Ammonites, and is 

 a member of the latter family. The edges of the 

 chamber-divisions in Ceratites are not so intricately 

 folded as in the Ammonites proper, and, singularly 

 enough, many of the young in some species of 



Fig. 313. Ammonites obtusns. Fig. 314. Side view of ditto. 



Ammonites pass through a Ceratite stage, in that 

 their sutures are less complex then than during their 

 adult life. 



About five hundred species of Ammonites have 

 been already figured and described, as occurring in the 

 formations from the Lias up to and including the 

 Chalk. Palaeontologists have roughly separated them 

 into six great groups as follows : (i) Those where 



