108 MEMOIRS OF THE UNIVERSITY OF CALIFORNIA 



Diagnosis. — Two flagella, one longitudinal, threadlike, usually posterior, 

 trailing, the other ribbon-like and held transversely; girdle and sulcus more 

 or less well developed ; contractile vacuole absent ; body either naked or covered 

 with a sculptured shell. Colonial organization in ephemeral or permanent 

 chain is sometimes found. The life cj^cle may show a greater or less extent of 

 pohanorphism. 



This subclass contains 2 orders. 



Key to Orders of the DINOFLAGELLATA 



1. Body either naked or with a bivalve shell, without well developed girdle or sulcus 



Adiniferidea nom. nov. 



2. Body either naked or covered with a sculptured shell, girdle and sulcus present at some stage 



of the life cycle Diniferidea Delage and Herouard 



Order DINIFERIDEA Delage and Herouard emend. 



Dinifera Bergh (1881&), p. 273. Family. 

 Diniferida Delage and Herouard (1896), p. 381. 

 Diniferida, Kofoid (1907a), p. 164. 

 Dinifera, Doflein (1911), p. 325. 

 Peridiniidea Poche (1913), p. 161. Suborder. 



Diagnosis. — This is a large group with a wide range of characteristics. The 

 body may be naked or covered with a plain or sculptured shell or theca, con- 

 tinuous or composed of discrete plates; girdle and sulcus are well developed 

 and always present at some i^eriod of the life cycle ; nutrition may be holophytic, 

 saprophytic, holozoic or parasitic ; colorless to highly colored ; ocelli and nemat- 

 ocysts sometimes present. The life cycle is usually complex, sometimes showing 

 two distinct stages. Division is typically oblique. Sexual processes still obscure 

 except in Noctiluca. Fresh water and marine. This order contains four tribes. 



Key to Tribes of DINIFERIDAB 



1. Body naked, girdle and sulcus distinct at some period of the life cycle. .Gymnodinioidae Poche 



2. Body with superficial or more deeply embedded skeletal elements, without enveloping cuirass 



Amphilothioidae nom. nov. 



3. Body naked without skeletal elements, girdle and sulcus suppressed 



Cystoflagelloidae nom. nov. 



4. Body with theca composed of a continuous membrane or of discrete plates, epitheca and 



hypotheca separated by the girdle plates Peridinioidae nom. nov. 



