128 The Mastigophora 



An interesting occurrence of Prymnesium pai-viim has been reported 

 in brackish fish-ponds in Palestine. Populations of the flagellates reached 

 500,000/ml. or more, changing the color of the water to a yellowish- 

 brown and resulting in death of many fish (241). 



Suborder 2. Silicoflagellina. These widely distributed marine flagellates 

 occur also as fossils from Upper Cretaceous to recent deposits. Their 

 taxonomic position was in doubt until Borgert (124) discovered the 

 flagellum and assigned them to a new group, the Silicoflagellata. Their 



Fig. 4. 9. Silicoflagellina. A-H. Skeletons of various species (after De- 

 flandre). A. Dictyocha crux, x560. B. D. octonaria, x560. C. D. triacantha 

 Ehrbg. from Tertiary, x345. D. D. navinda Ehrbg. from Tertiary, x345. 

 E. Vallacerta hortoni Hanna from Upper Cretaceous, x540. F. Dictyocha 

 speculum Ehrbg. from Tertiary, x630. G. D. polyactis Ehrbg. from Ter- 

 tiary, x630. H. D. fibula Ehrbg., x560. I. D. speculum, showing nucleus, 

 chromatophores, and internal skeleton; xl320 (after Deflandre). 



