2o6 NEW YORK STATE MUSEUM 



depressed. The surface bears a few simple filiform radial lines 

 along the body of the shell and others are visible on the posterior 

 wing at the hinge. No concentric lines are evident. 

 Lozver Devonic. Dalhousie, N. B. 



Pterinea intercostata nov. 



Shell suberect or oblique with small auricle and well defined, 

 broad but not extended posterior ear. Hinge straight, about two 

 thirds the greatest diameter of the shell. Beaks anterior, subter- 

 minal. Left valve with coarse and strong radial ribs separated by 

 broad flat interspaces. Of these one can count about 12 on the 

 body of the shell. The primary interspaces are usually divided by 

 a much finer median riblet but further subdivision is very unusuaL 

 On the broad posterior wing radial ribs are sparse and indistinct 

 though usually traces of them may be seen. Here the fine concen- 



/ m 



Pterinea intercostata 



trie lines predominate, giving the surface a smoothness in contrast 

 to the rest of the valve. The concentric lines are also visible on 

 the rest of the surface. As usually preserved they make faint 

 interruptions of the radial ribs but when normal are lamellose and 

 strongly defined. The right valve is practically devoid of radial 

 sculpture, the surface being crossed by sharply defined concentric 

 lines, only the posterior wing showing a few riblets on the cast. 

 The contrast in the markings of the two valves is extreme but is 

 conclusively demonstrated by several specimens with both valves- 

 retained. 



This species may be compared in respect to ornament with several 

 coarsely ribbed shells, e.g. P. costata Goldfs., A v i c u 1 a 



