Fig. 154. a, Plagiopyxis callida, X200 (Wailes);^b, Pontigulasia vas, 

 X200 (Cash); c, Phryganella acropodia, Xl90 (Cash); d, Bullinula 

 indica, Xl30 (Wailes); e, f, Heleopera petricola, Xl90 (Cash); g, Nadi- 

 nella tenella, X400 (Penard) ; h, Frenzelina reniformis, X600 (Penard) ; 

 i, Amphitrema flavum, X360 (Cash and Wailes); j, Pseudodifflugia 

 gracilis, X330 (Cash); k, Diaphoropodon mobile, X270 (Cash and 

 Wailes); 1, m, Clypeolina marginaia, X330 (Cash and Wailes). 



Genus Heleopera Leidy. Test variously colored; fundus hemi- 

 spherical, with sand-grains; surface covered with amorphous 

 scales, often overlapping; aperture truncate, narrow, elliptic 

 notched in narrow lateral view; a single nucleus; pseudopodia 

 variable in number, thin, digitate or branching; fresh water. Sev- 

 eral species. 



H. 'petricola L. (Fig. 154, e, /). Test variable in size and color, 

 strongly compressed; fundus rough with sand-grains of various 



