CLASS V 



CEPHALOPODA 



643 



Fro. 1222. 



Arcestes intuslahiatus Mojs, 4 Upper Trias ; Steinbergkogel, near Hallstadt, Austria. 

 A, B, Externaliaspect. C, Median section. D, Sutuje-line. 



finely divided, arranged serially. 

 The stems of the saddles are long 

 and narrow, divided anteriorly into 

 two or four branches. 



The shape and ornamentation 

 of the shell suggest a derivation 

 from Ayathiceras of the Carboni- 

 ferous and Permian, but no con- 

 necting links are known. 



Gladiscites Mojs. {Hypocladiscites 

 Mojs.) (Fig. 1225). Trias. 



Family 15. Meekoceratidae 



Waagen. 



Compressed discoidal and in- 



FiG. 1223. 



Joannites cymhiformis Wulfen. Upper Trias ; Raschberg, 

 near Aussee, Austria. Natural mould showing the living 

 chamber (after Mojsisovics). 



Fio. 1224. 



Suture-line of Didymitcs suhglobus 

 Mojs. Upper Trias ; Someraukogel, 

 near Hallstadt (after Mojsisovics). 



volute forms. Surface nearly smooth, radial folds being often present, but constrictions 

 and spines always absent. Body-chamber short. Septa simple goniatitic in primitive 

 forms, becoming ceratitic in most genera, but rarely reaching a digitate stage of com- 

 plexity in even the most specialised groups. The ventral lobe is divided in all forms ; 



