6 PROCEEDINGS OF THE NATIONAL MUSEUM vol.76 



numerous, rather coarse riblets of growth. Umbilicus filled but 

 apparently wide and deep. Aperture filled, apparently rounded and 

 extending very little below the base. 



The type (Cat. No. 371005, U.S.N.M.) measures: Greater diameter, 

 14 mm.; lesser diameter, 12 mm.; altitude, 63^ mm. 



This species may be closely related to Polygyra texasiana Moricand, 

 but is larger and the material filling the aperture makes it impossible 

 to say whether or not there were teeth. The species is named for 

 John C. Myers, of Houston, Tex., who sent the material on which this 

 paper is based. 



EXPLANATION OF PLATE 



Fig. 1. Pliconaias popenoei (beak sculpture), new species. X 2. 



2. Antediplodon dumblei Simpson (beak sculpture). X 5. 



3. Eonaias reynosenica, new species. 



4. Eonaias reynosenica (beak sculpture of paratype). X 2. 



5. Polygyra myersi (front view), new species. X 2. 



6. Eonaias reynosenica, new species. 



7. Antediplodon dewittensis, new species. 



8. Antediplodon dumblei Simpson. 



9. Pliconaias popenoei, new species. 



10. Polygyra myersi (top view), new species. X 2. 



o . 



