184 



BRACHIOPODA 



Stringocephalus (fig. 88). Shell smooth, circular or oval in 

 outline. Ventral valve with a sharp, prominent, incurved umbo; 

 area present. Peduncle-opening large in young individuals, but 

 smaller and oval in adults on account of the development of the 

 deltidium. Ventral valve with a median septum (vs), which extends 

 from the umbo almost to the front of the valve, and increases in 



Fig. 88. Stringocephalus burtini, Devonian. A, Dorsal valve. B, Profile. 

 a, adductor ; c, crura ; I, loop ; j, cardinal process ; p, hinge-plate ; 

 s, dorsal septum ; vs, ventral septum ; t, dental sockets. (From 

 Woodward.) x J. 



height towards the latter. Dorsal valve less convex, with a small 

 septum (s), and a long slightly curved cardinal process (j), divided 

 at its extremity to embrace the ventral septum. The brachial 

 skeleton consists of two branches (c) arising from the hinge-plate 

 (p), which pass to the middle of the shell and are then sharply bent 

 back and form a ring (I) parallel and near to the margin of 

 the valve. Devonian. Ex. S. burtini. 



Distribution of the Brachiopoda 



The Brachiopocls are all marine, and are found in all 

 parts of the world ; at the present time they are much 

 less numerous than in former periods of the earth's history, 



