EXPLANATION OF PLATE XLIII. 



Page 



FIG. 1. Monopteria longispina 1U 



Left valve. (Hare collection.) 

 Carboniferous, Upper Coal Measures. 



FIG. 2. Monopteria gibbosa 114 



2a. Right valve. 



2b. Anterior view of same. 



Carboniferous, Upper Coal Measures . 



FIG. %, Myalina swallowi 119 



3a. Right valve. 

 3b. Left valve. 

 3c. Dorsal aspect. 



Carboniferous, Upper Coal Measures . 



FIG. 4. Aviculopecten carboniferus Ill 



4a. Valve showing markings . 

 4b . Opposite valve . 



Carboniferous, Upper Coal Measures. 



FIG. 5. Myalina kansasensi* 117 



Shell showing imbricated lines of growth. (Calvin collection.) 

 Carboniferous , Upper Coal Measures . 



FIG. 6. Aviculopecten sp . 1 



Specimen with ears broken away. (Hare collection.) 

 Carboniferous, Upper Coal Measures. 



FIG . 7. Aviculopecten magna 110 



Medium- si zed specimen. (Shepard collection.) 

 Carboniferous, Burlington limestone. 



FIG. 8. Lithophaga sp. 1 116 



8a. Left valve. (Rowley collection.) 

 8b. Dorsal outline of same. 



Carboniferous, Lower Burlington limestone. 



FIG. 9. Placunopsis carbonaria 1(6 



Left side . (Hare collection . ) 

 Carboniferous, Upper Coal Measures. 



