EXPLANATION OF PLATE XVII. 



Fig. 1. Gi;ypiiea Pitcheri var. (Page 171.) 



a. Interior view of the convex or lower valve. 

 1). JCxterior view of the aame. 



c. Lateral view of tbo same, sbowiug the curvature. 



d. Less elongate example of a convex valve. 

 c. Exterior of upper or flat valve. 



/. Interior of tbe same. 

 Fig. 2. Exogyua i^sviuscula. (Page 173.) 



a. Lateral view of a moderately large example. 



b. Inner view of a smaller example. 



c. Lateral view of tlie same. 



d. External view of tbe same. 



Fig. 3. Exogyra costata var. fluminis. (Page 174.) 



a. Lateral view of tbe largest example in tbe collection. 



h. Dorsal view of tbe same. 



c. View of tbo flat valve connected with tbe deep one. 



(f. Exterior view of small example. 

 Fig. 4. Lijia Wacoensis. (Page 176.) 



a. Right valve, natural size. ■ 



h. Left valve of another example. ^ 



c. Lateral view of tbe same, showing its convexity. 

 Fio. .'■>. Camptoxectes pi.atessa. (Page 176.) 



a. Right valve. Tbe surface-markings mostly removed, and i-^e radiating striaj a little too 

 strong in the figure. 

 Fig. G. Mactra? inx'Ompta. (Page 185.) 



a. Right valve, enlarged one-half. 



b. Dorsal view of the same example. 

 Fig. 7. Corbola ni:matopiioka. (Pago 188.) 



a. Right valve, external view, enlarged. 



b. Left valve, external view, enlarged. 



c. Right valv(^, interior view, showing hinge. 



