SOME NEW DEVONIC FOSSILS 



287 



'Cation of the sharp riblets, an almost flat dorsal valve with low 

 "broad median depression and a medially elevated ventral valve 

 with broad not acute keel. It is closely similar to O r t h i s 

 tectiformis Walther, as cited, from the upper Coblentzian of 

 the Haiger. 



Lozver Devonic. Edmunds Hill, Chapman Plantation, Me. 



Orbiculoidea mentis nov. 



Shell very large, brachial valve highly elevated, suberect, much 

 longer on the posterior than on the anterior slope. Posterior 

 ■curvature concave beneath the arched beak ; in front of the beak 

 the surface is convex, the shell being uniformly expanded in the 



Orbiculoidea mentis 



pallial region. Marginal outline subcircular. Surface bearing fine 

 distant elevated concentric striae which may undulate and inoscu- 

 late. These are crossed by very fine radial lines which probably 

 do not pertain to the epidermal layer. 



The pedicle valve is concave exteriorly though the beak is ele- 

 vated and the pedicle slit does not extend to the margin. 



