CLASS II 



Eleiitherocrania von Huene 

 Ordovician ; Esthonia. 



BRACHIOPODA 379 



Biconvex Craniids related to Petrocrania. 



Cranismis reUifns (Quenst.). 

 Upper Jura ; Oerlinger 

 Thai, Wurtemberg. Interior 

 of ventral valve, i/i (after 

 Quenstedt). 



Fig. 559. 



Ancistritcrania parhiensis (Defr.). Upper Cretaceon.s ; France. 

 A, Prolile of dor.sal valve. B, Interior of same. ( ', Interior of ven- 

 tral valve, i/j. 



Craniscus Dall (Fig. 558). Ventral interior divided by septa into three 

 cavities. Jurassic ; Europe. 



Ancistrocrania Dall (Fig. 559). Dorsal valve with two muscular fulcra. 



Fig. 560. 



Isocrania ignabergt'iisis (Retzius). Uppermost Cretaceous ; Ignaberga, Scania, yl, Profile and dorsal aspect 

 of shell, i/i- B, C, Interior of ventral valve. D, Interior of dorsal valve, enlarged. 



Cretaceous ; Europe. Isocrania Jaekel (Fig. 560). Exterior plicate. 

 Cretaceous ; Europe. 



Pholidops Hall {Craniops Hall). Biconvex and but slightly attached 

 Craniids. Ordovician to Carboniferous ; North America, England, Gotland. 



Pseudocrania M'Coy (Palaeocrania Quenstedt). Eadially striated shells 

 much like Pholidops. Ordovician ; Europe. 



Cardinocrania Waagen. Permian of India. 



Order 3. PROTREMATA Beecher. 



Specialised (through atrematous Kutorginacea), articulate, calcareous 

 Brachiopoda, with well-developed cardinal areas. Exterior surface nearly 

 always either plicate, striate or spinous, and but rarely smooth. Pedicle 

 aperture restricted to the ventral valve throughout life and more or less 

 closed by a deltidium ; in some forms the pedicle is functional only in early 

 life and later the animals cement the ventral valve to foreign bodies. Chilidium, 

 spondylium and cruralium often present. Brachia unsupported by a calcai'eous 

 skeleton other than short crura. 



Superfamily 1. ORTHACEA Walcott and Schuchert. 



Progressive Profremata. The older genera have immature spondylia that are 

 rarely freely suspended but are commonly cemented directly to the valves ( = pseudo- 

 spondyUa). In the great majority of the later genera all traces of spondylia are lost. 



