232 MEMOIRS OF THE UNIVERSITY OF CALIFORNIA 



OccuRBENCE. — The exact occiuTence and distribution of this species is hard 

 to define, since it has been confused in literature with several other similar 

 forms, as may l^e seen in an examination of Schiitt's figures (1895, 1896), as 

 well as those of Dogiel (1906). It is aj^parently cosmopolitan in the marine 

 habitat, having been recorded as Pyrocydis from nearly every sea where dino- 

 flagellates have been studied. It is abundant at La Jolla in the surface plankton 

 during most of the summer. 



Syxonymy. — Claparede and Ijachmann (1858-61) early described these 

 cysts from Bergen, Norway, as developmental stages of Peridininm. First 

 figured by Schiitt (1895) as Gymnodinmm lunula, he later (1896) changed the 

 name of this species to Pyivrysfis lunula. Dogiel (1906) recommended its 

 inclusion in the genus Gymuodiiiiuni as G. lunula. Klebs (1912) further added 

 to the confusion already existing by creating for it a new genus, Diplodinium, 

 disregarding the fact that that name was already preoccupied by a ciliate in 

 the group Protista, Diploduuiim Schuberg. Following the usage of Schiitt 

 and the suggestion of Dogiel, we regard this species as a valid one in the genus 

 Gymnodimum, and base its allocation on the affinities revealed by the motile 

 biflagellate stage, as elsewhere in the Gymnodinioidae. It appears better to 

 await a fuller knowledge of life histories of Gymnodinium. before accepting 

 Pascher's (1916) allocation of this species in a separate genus as he has done 

 in erecting Dissodi)iiu)ii for it. 



Its affinities within the genus are obscured by our lack of knowledge of the 

 smaller representatives of this genus. It is close to the species G. scopulosum 

 in its sabconical form, but is much smaller (22^*) than that species (47/^), and 

 lacks its overhanging epitheca. 



Closer inspection of the spheroidal and cresentic cysts referable to this 

 species is needed to determine whether or not they may include phases of several 

 species. 



Gymnodinium marinum Saville-Kent 



Text figure X, 13 



Gymnodinium marinum Saville-Kent (1880-82), p. 444, pi. 25, figs. 60-61. 



G. marinum, Biitschli (1885), p. 1017. 



G. marinum. Entz, Jr. (1902), p. 123; (1907), p. 17: (1909), p. 253. 



Di.\f!xosis. — A uiinute species with broadly ovoidal liody, dorsoventrally 

 compressed, its length 1.03 transdiameters ; girdle premedian, without displace- 

 ment ; sulcus extending from girdle to antapex ; colorless, holozoic. Length, 30^. 

 Infusion of hay and sea water froui St. Heliers, Jersey, March. 



Description. — The body is broadly oval in ventral view with broad apices, widest posteriorly, 

 its length 1.03 transdiameters at the widest part. It is compressed dorsoventrally to about 

 0.62 of the widest transdiameter, and in lateral view is reniform with convex dorsal and concave 

 ventral surface. The hypocone exceeds the epicone in length and in width. The epicone is 

 hemispherical in ventral view with symmetrically rounded sides. Its length is 0.4 of the total 

 length of the body. The hypocone is hemispherical posteriorly, widest in the central part and 

 tapering anteriorly at the girdle, in ventral view. 



