98 HANDBOOK OF PROTOZOOLOGY 



include various diatoms, copepods and several pelagic animals. 

 The group is divided into three suborders as follows: 



Naked or with bivalve shell; without annulus or sulcus. .Suborder 1 Adinida 



Naked or with test; annulus and sulcus present at some stage 



Suborder 2 Dinifera 



Naked without annulus or sulcus; without transverse flagellum 



Suborder 3 Cystoflagellata 



Suborder 1 Adinida Bergh 



Test bivalve; without any groove; with yellow chromato- 

 phores. Two flagella arise from the anterior end; one directed 

 anteriorly, the other vibrates in a circle. Fresh and salt waters. 

 Several genera. 



Genus Exuviaella Cienkowski. Subspherical or oval. No 

 anterior projection, except two flagella. Two lateral chromato- 

 phores, large brown, each with a pyrenoid and an amylum body. 

 Nucleus posterior. Marine. Several species. 



Exuviaella marina Cienkowski (Fig. 34, a, b). About 80 

 microns long. 



Genus Prorocentrum Ehrenberg. Elongated oval; anterior 

 end is bluntly pointed, with a spinous projection at the end. 

 Chromatophores small, yellowish brown. Marine. 



Prorocentrum micans Ehrenberg (Fig. 34, c). About 50 mi- 

 crons long. The cause of "red water." 



Suborder 2 Dinifera Bergh 



Typical Dinoflagellida with one to many transverse annuli 

 and a sulcus. There are two flagella, one of which undergoes a 

 typical undulating movement, while the other is usually directed 

 posteriorly. According to Kofoid and Swezy, this suborder is 

 divided into two tribes. 



Body covered by a thick shell . Tribe 1 Peridinioidae 



Body naked or covered by a thin shell Tribe 2 Gymnodinioidae 



Tribe 1 Peridinioidae Kofoid and Swezy 



The shell is composed of epitheca, girdle, and hypotheca, 

 which may be divided into numerous plates. Body form various. 



With annulus and sulcus 



Shell composed of plates; but no suture Family 1 Peridiniidae 



Breast plate divided by sagittal suture Family 2 Dinophysidae 



Without annulus or sulcus Family 3 Phytodiniidae 



