PLATE 15. 



Page 



Figs. 1-5. Strophodonta concava 96 



1. Interior of the dorsal valve of a young individual, sliowing the muscular impressions, cardi- 



nal process, socket plates and crenulated hinge; enlarged to two diameters. 



2. Interior of a deeply concave dorsal valve, showing very large socket plates. 

 8. Profile of specimen, fig. 2. 



4. Enlargement to two diameters of the central part of an adult dorsal valve showing the mus- 

 cular impression, cardinal ))rocess, socket plates and crenulated hinge. 



6. Cardinal view of the specimen, fig. 4, showing the elevation of the cardinal process and 

 socket plates, crenulated hinge, and the absorption of the base of the cardinal process, 

 to accommodate the margin of the opposite valve j enlarged to two diameters. 



Fig. 6. Steophodonta pateksoni 89 



6. Interior of the dorsal valve of a specimen, referred with some doubt to this species. 



Figs. 7, 8. Strophodonta pkrplana 98 



7. Interior of a dorsal valve, showing the muscular impression, cardinal process and crenulated 



binge. 



8. Cardinal view of specimen, fig. 7, showing the elevation of the cardinal process. 



Figs. 9, 17. Strophodonta junia = S. textilis of text 108 



9. E.xterior of a ventral valve, from the TuUy limestone. 



17. Cardinal view of a specimen, showing hinge area, deltidiuni, etc. 



Figs. 10, 11. Strophodonta inequistriata 106 



10. Interior of a ventral valve, showing the arrangement of the muscular impressions; enlarged 



to two diameters. 



11. Enlargement of an imperfect dorsal valve, showing the highly elevated muscular impres- 



sions, cardinal process, etc. 



Fig. 12. Strophodonta scbdemissa 414 



12. Interior of a dorsal valve of this species, from the Hamilton group of Iowa. 



Figs. 13, 14. Strophodonta mucronata Ill 



13. A ventral valve, showing mucronate extensions of the cardinal extremities. 



14. A dorsal view of a specimen without mucronate extensions. 



Figs. 1.5, 16. Strophomena rhomboidalis ? 414 



15. Exterior of a ventral valve, from the Waverly sandstone series of Ohio 



16. Interior of a dorsal valve, showing the muscular impressions, cardinal process, etc., from 



the Waverly sandstones of Ohio. 



