CLASS V 



CEPHALOPODA 



643 



Fio. 1222. 



Arcestes intuslabiatus Mojs. Upper Trias ; Steinbergkogel, near Hallstadt, Austria. 

 A, B, Externa! aspect. C, Median section. D, Suture-line. 



Fig. 1223. 



Joannites cymhiformis Wulfen. Upper Trias ; Raschberg, 

 near Aiissee, Austria. Natural mciild showing the living 

 Chamber (after Mojsisovics). 



finely divided, arranged serially. 

 The stems of the saddles are long 

 and narroiv, divided anteriorly into 

 two or four branches. 



The shape and ornamentation 

 of the Shell suggest a derivation 

 from Agathiceras of the Carboni- 

 ferous and Permian, biit no con- 

 necting links are known. 



Gladiscites Mojs. (Hypocladiscites 

 Mojs.) (Fig. 1225). Trias. 



Family 15. Meekoceratidae 

 Waagen. 



Gompressed discoidal and in- 



Fio. 1224. 



Suture-line of Didymites suhglohus 

 Mojs. Upper Trias ; Someraukogel, 

 near Hallstadt (after Mojsisovics). 



volute forms. Surface nearly smooth, radial folds heing 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 ; 



