ORDER III NEOTREMATA—PROTREMATA Sil 
Family 1. Craniidae. King. 
Crania, Retzius (Fig. 514). Shell inequivalve, sub-cireular 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 

Fia. 514. 
Crania Ignabergensis, Retzius. Uppermost Cretaceous ; Ignaberga, Scania. A, Profile and dorsal aspect of 
shell, 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. 
(2) Ordovician and Devonian ; North America and Europe. 

Fie. 515. 
Craniscus velata, Quenst. . 
Upper Jura; Oerlinger Thal, eee PUG 
Wiirtemberg. Interior of Ancistrocrania Parisiensis, Defr. Upper Cretaceous; France. 
ventral valve, 1/; (after A, Profile of dorsal valve. 2B, Interior of same. C, Interior of 
Quenstedt). ventral valve, 1/;. 
Craniscus, Dall (Fig. 515). Ventral interior divided by septa into three 
cavities. Jurassic ; Europe. 
Ancistrocrania, Dall (Fig. 516). Dorsal valve with two muscular fulera. 
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.  Prodeltidium 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. 
