KOFOID AND SWEZY: UNARMORED DINOFLAGELLATA 219 



characteristic of Ampliidinium, one of its associates in that habitat. It was 

 fouucl in company with Aiuphidinium scission, A. trinicatum, A. corpulentum, 

 and A. usymmctricnm. It belongs in the subgenus Lineadinium, but is whoUy 

 unlike any other species. The apical hook is homologous with that found in 

 G. vestifici, but there are wide differences in the proportions of the body between 

 these two species. In form, proportions, and apical hook it is close to G. agile 

 sp. nov. (fig. Y, 9), but this species is larger, lacks striae, and has chromato- 

 phores. 



Gymnodinium helveticum Peuard 



Text figure Y, 11 



Gymnodinium helveticum Penard (1891), pp. 6, 21, 22, 47. 58, 59, pi. 5, figs. 10-16. 



G. helveticum, Imhof (1892), p. 175. 



G. helveticum. Lemmermann (1900), p. 116; (1902), p. 260; (1910), pp. 613, 618, 619, 



621, figs. 17-19. 

 G. helveticum, Lauterborn (1910), p. 471; (1913), pp. 864, 902, 906. 

 G. helveticum, Schilling (1913), p. 20, fig. 20. 

 G. helveticum, West (1916), p. 53. 



DiAGXosis. — A small species witli subu^oidal Ijudy, it.s length 1.66 transdiani- 

 eters ; girdle premedian, displaced its own width ; sulcus invading both epicone 

 and hypocone ; sm-f ace sti'iate ; color, rose. Length, 50m. Lake Geneva, Switzer- 

 land, Ehine River, Germany. 



Description. — The body is symmetrically siibovoidal. widest anteriorly at the girdle, tapering 

 posteriori}', its length 1.66 transdianieters at the widest part. The epicene is shorter than the 

 hypocone by about 0.37 of its length. It is subconical, about 70°, with rotund sides. The apex 

 is acuminate-truncate with three minute, pointed projections, the middle one being about twice 

 the height of the other two. The epicone has a length on the left and right sides of 0.36 and 

 0.4 respectively of the total length of the body. The hypocone is conical, about 55°, with a 

 slender, acuminate antapex. 



The girdle is premedian in position, its proximal end joining the sulcus at a distance from 

 the apex of 0.36 and its distal end 0.4 of the total length of the body. The furrow is wide, about 

 0.1 transdiameter, its proximal end about half that width and its distal end almost obscured 

 by the overhanging proximal border. Its depth is about 0.3 radius and its sides form an obtuse 

 angle with the surface of the hypocone and an acute one with the surface of the epicone. The 

 sulcus begins just below the apex and extends posteriorly in an almost straight line to within a 

 short distance of the antapex. Its borders in the posterior part are drawn out into two pointed 

 flaps, the one on the right side much nearer the antapex than the one on the left. The longi- 

 tudinal flagellum arises at the junction of the girdle and sulcus. The transverse flagellum was 

 not observed by Penard (1891). 



The nucleus is an ellipsoidal body found in the middle of the body in the region of the union 

 of girdle and sulcus. Its long axis is jjarallel with the long axis of the body. It is filled with 

 coarse, chromatin strands lying parallel with its major .axis. Its major and minor axes are 

 about 0.53 and 0.28 transdiameter respectively in length. 



The cytoplasm is clear, with numerous refractive granules in the peripheral zone. The 

 general color of the organism is the rose color of the peach blossom. A small spherical pusule 

 is found immediately behind the point of union of girdle and sulcus. The surface is covered 



