244 Systematic Paleoxtology— Middle Devoxian 



Palaeoxeilo clarkei n. sp. 

 Plate XXVII, Figs. 10-13 



Description. — Shell large, elongate-ovate; length somewhat less than 

 twice the height; basal margin nearly straight or slightly concave near 

 the middle. Anterior end rounded; posterior end truncate to slightly 

 rounded. Valves convex, the greatest convexity along the middle line 

 and near the uinljo; the left valve crossed by a shallow sinus which ex- 

 tends obliquely from the umbo about to the middle of the basal margin, 

 apparently not so conspicuous on the right valve; beaks at about the an- 

 terior third. Test thin, and apparently marked with medium sized con- 

 centric striae which extend from the anterior to the posterior end. Hinge 

 marked by numerous crenulations or taxodont teeth, which are coarser 

 toward the posterior extiemity. 



The specimens are more or less completely exfoliated so that it is 

 difficult to describe their surface characters. The species is distinguished 

 by its elongate form, striae and shallow sinus. 



Length, 30-34 mm.; height, 1()-19 mm. 



Named in honor of Dr. John M. Clarke. 



Occurrence. — Eomxey Formatiox, Hamilton Member. W. Va. 

 side Potomac Eiver about 3 miles south of Cumberland. 



Collection. — Maryland Geological Survey. 



Palaeoxeilo eowei n. sp. 

 Plate XXVII, Figs. 14, 15 



Description. — Shell large, elongate-ovate and very gibbous in the 

 umbonal region; length considerably less than twice the height; basal 

 margin curving and anterior end rounded. Valve strongly convex espe- 

 cially toward tlie umbo ; beak prominent and near the anterior end. Sur- 

 face markings unknown. Anterior and posterior muscular impressions 

 strongly marked, hinge marked by numerous crenulations apparently of 

 about equal strength. 



The above description is based upon an internal impression of a left 

 valve from the Xational Eoad i,4 mile west of Tonolowav Eidge ; but the 



