PLATE 15. 
Page 
Figs. 1-5. Strophodonta concava ...... 96 
1. Interior of the dorsal valve of a young individual, showing 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. 
3. 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 process, socket plates and crenulated hinge. 
5. 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; enlarged to two diameters. 
Fig. 6. Strophodonta patersoni.... 89 
6. Interior of the dorsal valve of a specimen, referred with some doubt to this species. 
Figs. 7, 8. Strophodonta perplana...... 98 
7. Interior of a dorsal valve, showing the muscular impression, cardinal process and crenulated 
hinge. 
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. Exterior of a ventral valve, from the Tully limestone. 
17. Cardinal view of a specimen, showing hinge area, deltidium, 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 subdemissa. 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. 15, 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. 
