PELECYPODA—PRIONODESMACEA. 447 



surface marked by concentric striae. Upper Devonic to Missis- 

 sippi. 



227. P. profundus Hall. (Fig. 589.) Devonic. 

 Umbonal region gibbous. Anterior ear acute. Posterior ear 



not defined. Surface covered with concentric striae which rise at 

 intervals into undulations. 

 Chemung : New York. 



LXX. Actinopteria Hall. (Avicula Bruguiere of American 



authors in part.) 

 Inequivalve, oblique, thin. Anterior muscle scar faint or ab- 

 sent. Pallial line simple. Differs from Pterinea in the absence 

 of a broad striated ligament area and strong cardinal and lateral 

 teeth. Devonic. 



228. A. communis Hall. Devonic. 

 Differs externally from Pterinea flab ellum in its smaller anterior 



ear, weaker rays of both sizes which are practically absent from 

 both ears, finer concentric striae, and in the greater similarity of 

 the surface marking on the two valves. 



Helderbergian : Maine, New York (New Scotland), New Jer- 

 sey, Tennessee. 



229. A. textilis Hall. (Fig. 590.) Devonic. 

 Externally very similar to Pterinea flabelhim ; distinguished by 



the greater strength of its intermediate rays and by its longer 

 posterior wing and greater obliquity. 



Fig. 590. Actinopteria textilis. (Pal. N. Y., III.) 



Helderbergian : New York. Oriskany : New York, New Jer- 

 sey, Tennessee ?, New Brunswick. 



