Ammonoidea — Ammonites. 



33 



Muschelkalk species, Ceratites nodosus, with its peculiar suture- GALLERY 

 line (Fig. 57), and the richly ornamented shell of Trachyceras Aoti 

 (Fig. 58), are met with. In the Cladiscitid^ may be mentioned gg^ 

 the genus Cladiscites, often ornamented with closely-set spiral 

 ridges. 



Fig. 57. — Ceratites nodosus, De Haan. Muschelkalk. 



Three very peculiar shells also deserve notice. They are 

 Chorutoceras, Cochloceras, and Rhahdoceras. In Choristoceras, the 

 last whorl becomes separated from the preceding ones, in the 

 manner of Crioceras. Cochloceras is turreted like a Gasteropod, 



Fig. 58. — Trachyceras Aon, Miinst. Alpine Trias. 



and may be compared with Turrilites in this respect. Rhahdoceras 

 is straight, like Baculites. All are from the Alpine Trias. 



The PusTACOCERATiD^ coutaiu the large species known as Pinaco- Wall- 

 ceras Metternichi, from the Keuper of Hallstadt, in Upper Austria. °**® ^^' 



