BRACHIOPODA 



53 



strata to the trias. Uncites gryphus (fig. 11, 6), a peculiar De- 

 vonian fossil, has a prominent beak, perforated in the young- 

 shell by a minute apical foramen ; the hinge-area is filled up 

 by a deeply concave deltidium, on each side of which (but 

 only in some specimens) there is a lateral pouch formed by an 

 inflection of the margin of both valves. 



Fig. 12. 

 Brachiopoda. 



i. Orthis hysterita, L. (cast) ; Devonian, Rhine. 



2. Davidsonia Verneuili, Boucli ; Devonian, Eifel. 



3. Strophornena rhomboidalis, Wahl. ; U. Silurian, Dudley. 



4. Producta semi reticulata, Martin ; Carboniferous, Derbyshire. 



5. Chonetes striatella, Dalm. ; U. Ludlow rock, Herefordshire. 



6. Calceola sandalina, Lam. ; Devonian, Eifel. 



7. Obolus Apollinis, Eichw. ; L. Silurian, Northern Europe. 



8. Siphonotreta unguiculata, Eehw. ; U. Silurian, Britain. 



The family Orthidee consists of shells with a straight hinge- 

 line, bordered by a flat, narrow area, with a central notch in 

 each valve ; the ventral valve is furnished with articulating 

 hinge-teeth, and the dorsal valve has short processes for the 

 support of the oral arms, which appear to have been horizon- 

 tally spiral (as in AtrypcbS. Between the oral processes there 

 is a central projection for the attachment of the cardinal 

 muscles. Internal moulds of the Orthis (fig. 12, 1) exhibit on 



