BRACHIOPODA. 



337 



with the inner spiral appendages of the Spirifer, the outer 

 appearance of the smooth species, as T. tumida, circe, 

 and concentrica. 



Martinia. M'Coy. (Keticularia M ( Coy.) — Shell with 

 the hinge line shorter than the width of the shell ; dorsal 

 edges of the cardinal area obtusely rounded ; surface 

 smooth ; spiral appendages small. 



These shells are separated from Atrypa by there being 

 an area with a free deltidium. The genus includes Tere- 

 bratula rostrata, glabra, hyalina, lineata, and Icevigata. 



Stringocephalus. Defrance. — Shell free, fibrous, 

 oval or round, transverse, gibbose, inequivalve; upper 

 valve very large, convex, with a triangular area extending 

 from the hinge to the point of the incurved produced beak 

 lower valve much shorter, convex, with no area, and its 

 apex usually concealed; opening round, placed in the 

 middle of the length of a broad triangular deltidium 

 formed of two pieces joined together, and which separates 

 the opening from the lower valve; internal apparatus, 

 one strong medial plate on the upper valve, with sometimes 

 two other smaller plates ; the lower valve has on the 

 medial line a strong apophysis terminating in a fork, and 

 also two ribs rising from the sides of the hinge, and 

 converging towards the middle of the valve, where 

 they terminate in a long branch bent towards the upper 

 valve. 



The type of the genus is S. Burtoni, besides which, a 

 few others have been found in the Devonian strata. 



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