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PLATE 18. 
Fig. 6.—Heterodinium rigdenae, ventral view. X 410. ap. p-, apical pore; 
in fl. p., flagellar pore; l. f., longitudinal furrow; v. a., ventral 
F area; v. p., ventral pit. 
Fig. 7.—Dorsal view of the same. X 410. 
Fig. 8.—View of left side of same. X 410. 
Fig. 9.—Ventral view H. inaequale. X 420. Abbreviations as in fig. 6. 
Fig. 10.—Oblique view of right side of same. X 420. 
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