82 
IOWA ACADEMY OF SCIENCE Voi,. XXIX, 1922 
% 
PLATE II 
Zygospira variabilis fountainensis var. nov. 
1-3. Brachial, pedicle, and lateral views of a cotype, showing the 
even, rounded plications and median furrow (X2.5). 
Zygospira calhounensis sp. nov. 
4-6. Brachial, pedicle, and lateral views of a cotype, showing the 
differences between this species and Z. variabilis fountainensis 
^ (X2.5). 
Zygospira variabilis sp. nov. 
7-9. Brachial, pedicle, and lateral views of the holotype (X3). 
7a. Pedicle view of the holotype; cf fig. 2 (X1.8). 
Rhynchotrema uniplicatmn sp. nov. 
10-12. Brachial, pedicle, and lateral views of the oldest cotype. Note 
the single plication of the sinus and the nodose plications of both 
valves. 
13. Pedicle view of a younger cotype. 
Rhynchotrema dentatum (Hall) 
14-16. Brachial, pedicle, and lateral views of a typical Richmond speci- 
men, showing the differences between this species and R. unipli- 
catum. 
Rhynchotrema mercerense sp. nov. 
17-19. Brachial, pedicle, and lateral views of the larger of the cotypes. 
20-21. Brachial and lateral views of the smaller cotype. 
Rhynchotrema missouriense sp. nov. 
22-23. Brachial and pedicle views of the larger cotype, showing the 
coarse, rounded plications. 
26. Lateral view of the same specimen. 
24-25. Brachial and pedicle views of the smaller cotype.. 
Unless otherwise stated , all figures are enlarged about 1.5 diameters. 
