ORDER III 



NEOTREMAT A PROTREMATA 



311 



Family 1. Craniidae. King. 



Crania, Eetzius (Fig. 514). Shell inequivalve, sub-circular in outline. In 

 the interior of both valves are two pairs of large adductor scars, the posterior 

 of which are widely separated and often strongly elevated on a central 



FIG. 514. 



Crania Ignabergensis, Retzius. Uppermost Cretaceous ; Ignaberga, Scania. A, Profile and dorsal aspect of 

 shell, 1/1. B, C, Interior of ventral valve. D, Interior of dorsal valve, enlarged. 



callosity. Impressions of the pallial genital canals coarsely digitate. Ordo- 

 vician to Recent ; maximum development in Ordovician and Cretaceous. 



Craniella, Oehlert. Large Cranias with S-shaped vascular impressions. 

 (?) Ordovician and Devonian ; North America and Europe. 



FIG. 515. 



f'l-niiisi'iis rel'/t", Quenst. 

 Upper Jura; Oerlinger Thai, 

 Wurtemberg. Interior of 

 ventral valve, Vl (after 

 Quenstedt). 



FIG. 516. 



Ancistrocrania Parisiensis, Defr. Upper Cretaceous ; France. 

 A, Profile of dorsal valve. B, Interior of same. C, Interior of 

 ventral valve, Vi- 



Craniscus, Dall (Fig. 5^5). Ventral interior divided by septa into three 

 cavities. Jurassic ; Europe. 



Ancistrocrania, Dall (Fig. 516). Dorsal valve with two muscular fulcra. 

 Cretaceous ; Europe. 



Pholidops, Hall (Craniops, Hall). - Biconvex and but slightly attached 

 Cranias. Ordovician to Carboniferous ; North America, England, Gottland. 



Pseudocrania, M'Coy (Palaeocrania, Quenstedt). Radially striated shells 

 much like Pholidops. Ordovician ; Europe. 



Cardinocrania, Waagen. Permian of India. 



Order 3. PROTREMATA.' Beecher. 



Articulate Brachiopoda, with the pedicle opening restricted to the ventral 

 valve throughout life or during early growth. Prodeltidittm originating on the 

 dorsal side of the body wall in the Cephalula stage, and later anchylosed to the ventral 

 shell, thus initiating the development of a deltidium. Pedicle aperture modified by 

 the deltidium. Brachia unsupported by a calcareous skeleton except in Pentameracea, 

 where there are crura. 



