KOFOID AND SWEZY: UNARMORED DINOFLAGELLATA 111 



Dinoflagellata. Pending the demonstration that they have in their life cycle 

 a true dinoflagellate phase it seems best to hold them in suspense. We have 

 accordingly omitted detailed treatment of this family in this monograph. 



The genera Cystodinium and Hypnodinium of Klebs (1912) appear to share 

 with Glenodinium the peculiarity of having a thin structureless theca closely 

 adherent to the cyto])lasm in the free stage where kno-^m. We therefore exclude 

 them from the Gpnnodinioidae and from this monograph. 



Key to the Families of the Tribe GYMNODINIOIDAE 



1. Girdle and sulcus feebly developed, both flagella nearly threadlike, not parasitic, no 



tentacle, no ocellus, no cell membrane, not permanently colonial 



Protodiniferidae fam. nov. 



1. Girdle and sulcus well developed, transverse flagellum ribbon-like, permanently colonial 2 



2. Not permanently colonial 3 



2. Permanently colonial, with nematocysts Polykrikidae fam. nov. 



3. No ocellus 4 



3. Ocellus present Pouchetiidae fam. nov. 



4. No tentacle 5 



4. Tentacle present, no ocellus Noctilucidae fam. nov. 



5. Not parasitic Gymnodiniidae Poche 



5. Parasitic at some stage Blastodiniidae fam. nov. 



Family 1. PROTODINIFERIDAE fam. nov. 



DiAGXosis. — G^nnnodinioidae with rudimentary girdle and sulcus; flagella 

 anterior or ventral; ocellus lacking; tentacle more or less well developed. 

 Length. 10/^ to 50m. Marine ; neritic from warm temperate waters ; 2 genera. 



De-scription. — This family contains representatives of the mast primitive G>-mnodinioidae 

 and forms a connecting link between the Diuiferidae and the Adiniferidae. The rudimentary 

 girdle and sulcus and the anterior or ventrolateral position of the flagella, as distinct from the 

 entire absence of girdle and sulcus and the anterior position of the flagella in the Adiniferidae, 

 links this family with the Diuiferidae rather than with tlie more primitive Adiniferidae. 



In the development of the girdle and sulcu.s in this family two distinct stages are present. 

 In Protodinifer these structures are found as the merest rudiments anteriorly located, with the 

 girdle less than one-half the circumference of the body in length and faintly outlined. In 

 Oxyrrhis the girdle or groove is ventrolateral and extends nearly or quite around the body, with 

 a well defined border on the anterior margin, the posterior one sloping away to the narrowed 

 posterior region of the body. In Protodinifer a tentacle springs from the sulcal region and 

 extends anteriorly some distance beyond the apex of the body. In Oxyrrhis the tentacle-like 

 projection also arises from the sulcal area in the region of tlie two flagellar pores, but its length 

 seldom exceeds one-half the distance between the pores and the antapex. It also appears to be 

 attached to the sulcal area for part of its length. The origin and position of the two structures 

 are essentially the same in both genera. 



