Bull. U. S. F. C. 1899. (To face page 104.) 
Plate 20 . 
Fig. 30. Distyla ohioensis Heriick. Dorsal view. (X 640.) 
Fig. 31. Distyla stokesii Pell. Dorsal view of lorica, showing the 
arrangement of the facets. (X 460.) 
Fig. 32. Distyla ludwigii Eckstein. Dorsal view of lorica (X 385.) 
Fig. 33 Distyla gissensis Eckstein. Dorsal view of partially ex- 
tended animal. (X 315.) 
Fig. 34. Distyla gissensis Eckstein. Dorsal view of completely re- 
tracted animal. (X 315.) 
Fig. 35. Monostyla cornuta Ehr. Ventral view. (X 365.) 
Fig. 36. Monostyla cornuta Ehr. Side view. (X 365.) 
