106 
Plate IV 
Rhynchotrema windermeris n. sp. 
Figure 1 . View of pedicle valve. (Page 20.) 
Figure 2. Interior of the pedicle valve, showing the deltidial plates characteristic of the genus. 
(Page 20.) 
Figure 3. Brachial valve, broken. The interior of the upper part is shown in figure 4. (Page 20.) 
Figure 4. Interior of the brachial valve, showing the rather wide, slightly raised, crural cavity. 
(Page 20.) 
Rhynchotrema increbescens (Hall) 
Figure 5. Interior showing the grooves of the crural plates and the long, tongue-like projection 
with the bifid end. X 4. (Page 21 .) 
Rhynchotrema increbescens occidens n . var. 
Figure 6. Pedicle valve. (Page 21.) 
Figure 7. Profile of both valves. (Page 21.) 
Figure 8. Interior of pedicle valve, showing dental plates and part of one tooth. X4. (Page 21.) 
Figure 9. Interior of brachial valve showing crural plates, short cavity, and minute cardinal 
process. A small piece of the pedicle valve is present and one tooth in the socket on right 
hand side. X4. (Page 21.) 
Figure 10. Interior of brachial valve at an angle, showing relationship of crural plates and septum. 
X 4. (Page 21.) 
Rhynchotrema pisina n. sp. 
Figure 11. Profile view showing the great convexity of the brachial valve and the relationship 
of the beaks. X 2. (Page 22.) 
Figure 12. Brachial valve showing the small, round form and the inconspicuousness of the fold. 
X 2. (Page 22.) 
Figure 13. Interior of the brachial valve, showing crural plates and ornamentation. X 4. (Page 22.) 
Rhynchotrema kananaskia n. sp. 
Figure 14. Brachial valve. (Page 23.) 
Figure 15. Pedicle valve. (Page 23.) 
Figure 16. Profile view showing the rather flattened outline of the brachial valve after the 
greatest complexity is reached. (Page 23.) 
Figure 17. Hinge view, showing the relationship of the beaks. (Page 23.) 
Figure 18. Part of a specimen magnified to show the ornamentation. X 4. (Page 23.) 
Plectorthis sinmtis n. sp. 
Figure 19. Brachial valve, showing a part of the area of the pedicle valve. (Page 23.) 
Figure 20. Pedicle valve, a little crushed on the left side. (Page 23.) 
Figure 21. Anterior view showing the sinuate outline of the margin. (Page 23.) 
