EXPLANATION OF PLATES. 
PLATE 17. 
1.—Heterodinium scrippsi ventral view. X 725. ap. p., apical pore; 
fl. p., flagellar pore; l. f., longitudinal furrow; v. a., ventral 
area; v. p., ventral pit. 
2.—Dorsal view of same. X 420. 
3.—Oblique view of left side of same. X 420. 
4.—Diagrammatie apical view of same. X 420. 
5.—Reticulations adjacent to posterior list of transverse furrow. 
xX 2725. 
[364] 
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