14 



MEMOIRS OF THE UNIVERSITY OF CALIFORNIA 



post. 



and OrnitJiocercus. It is in the non-tliecate forms that the developmeut aud 

 fundamental relations of the furrows may be most clearly seen. 



These furrows are two distinct structures, the more conspicuous of which 

 is the farrow or girdle passing around the body in a transverse direction (fig. 

 B, gir.). Its course is that of a descending left- wound spiral, with the ends 

 usually more or less widely disjilaced. The second furrow is a longitudinal 

 one, the sulcus, connecting the ends of the girdle, sometimes continuing on to 

 the apices (fig. B, sulc). Its course is morphologically longitudinal and in 



most of the genera its increasing 

 length keeps pace with the increasing 

 torsion of the body. This gives it a 

 spiral path around the body in the 

 more highly specialized members of 

 the group, as in CocModiniiun (figs. 



gg,"hh). 



These two structures, the girdle 

 and sulcus, are usually present at 

 some period of the life cycle of nearly 

 every member of the Dinoflagellata 

 outside of the Adiniferidea. In the 

 latter the furrows are entirely lack- 

 ing. In the genus Protodinifcv, the 

 most primitive of the Diniferidea 

 (fig. R, 2), the girdle is merely incip- 

 ient, short and poorly developed, its 

 length being less than 0.3 transdiam- 

 eter of the body. The sulcus con- 

 nected with it is also short and feebly 

 developed, and is occupied posteriorly 

 by a stout, rodlike tentacle, which 

 projects a short distance beyond the 

 body. The jimction of the proximal end of the girdle and sulcus here, as in the 

 tj^ical dinoflagellates, is occupied by the anterior pore from which issues the 

 transverse flagellum. The transverse flagellum in Protodinifer occupies the 

 girdle and continues its course aroimd the body beyond the incipient girdle, its 

 length frequently being greater than one complete turn. In the members of 

 the Adiniferidea, such as Prorocentrnm and Haplodinium, the anterior ex- 

 tremity of the body is marked by a shallow notch from which arise the two 

 flagella (figs. R, 5, 7), without any indication of a girdle. 



In the Diniferidea the girdle and sulcus are thus the outstanding features. 

 In Oxyrrliis, a second primitive genus, the girdle is posteriorly located, its 

 proximal border well developed, but not its distal one, resulting in a wide de- 

 pression of the posterior portion of the body (fig. R, 3). The typical form of 

 the girdle is first attained in the Gymnodiniidae, where it is usually complete 



long, fl 



Fig. B. Gyrodiiiium coraUinum sp. nov. Abbrevia- 

 tions: ant. p., anterior pore; epi., epicone; gir., girdle; 

 hyp., hypocone; interc. a., intereingular area; Jong, fl., 

 longitudinal flagellum; n., nucleus; pig., pigment; post, p., 

 posterior pore; pus., pusule; suJc, sulcus; tr. fl., trans- 

 verse flagellum. X 500. 



