KOFOID AND SWEZY: UNARMORED DINOFLAGELLATA 375 



Description. — Tlie body is ovoidal, soiiiewliat flattened ventrally, widest 0.65 total length 

 from apex. The dorsoventral diameter is 0.84 the trausdiameter, which is greatest slightly 

 below the middle. The epicene exceeds the hypocone by 0.15-0.20 total length. Its length at 

 the proximal and distal ends of the girdle is 0.28 and 0.86 total length respectively. It is rotund, 

 subconical (40°), with rounded apex. The hypocone has a length at the proximal and distal 

 ends of the girdle of 0.72 and 0.14 total length respectively. It is wider and fuller than the 

 epieone, flattened hemispherical, and its postmargin is indented by a broad sulcal notch. 



The girdle forms a descending left .spiral of 1.5 turns. It leaves the anterior junction with 

 the sulcus at 0.28-0.39 total length from the anterior end and is but slightly deflected in the 

 first 0.5 turn, then steepens to 30°-35°, increasing to 45° near the distal end. Its total dis- 

 placement is 0.50-0.57 of the total length. The furrow is moderately impressed, with distinctly 

 lined edges and slightly overhanging lips. Its width is about 0.1 trausdiameter. The sulcus 

 begins near the apex on the epieone, runs thence posteriorly with slight torsion to its anterior 

 junction with the girdle 0.28-0.39 total length from the anterior end, descends with increasing 

 torsion in a steep left spiral of about 0.5 turn to the distal junction 0.14-0.18 total length from 

 the posterior end. In the lower part of the intercingular section it is very close to the girdle. 

 It is a narrow trough about 0.5 width of the furrow and does not lie in a depression of the 

 surface produced by its constriction. Below the posterior junction it flares widely and broadly 

 notches the pastmargin. The anterior flagellar pore lies at the anterior junction and the 

 posterior pore some distance below the posterior one. The transverse flagellum runs the whole 

 length of the girdle and the posterior one is less than a trausdiameter in length (in the cj'st). 



In both Schiitt's (1895) specimen and our own the nucleus was peculiar in that it was stout 

 reniform in outline with more or less concentric, spiral, moniliform chromatin threads. It lies 

 to the right and near the middle of the body or below it. Its major and minor axes in our 

 specimen were 0.9 and 0.5 transdiameter respectively, in Schiitt's specimen (1895), 0.54 and 

 0.40 respectively. In Schiitt's figure (1895) there is a food mass anteriorly and a cluster of 

 twisted rodlets near the apex. The plasma of our specimen was clear, without formed contents 

 of either of these kinds. An anterior sack-shaped pusule opens anteriorly into the pore of the 

 transverse flagellum. No posterior pusule was noted. Schiitt (1895) apparently figures both, 

 but does not label them. In the peripheral plasma is a layer of circular ochraceous platelets 

 resembling chromatophores in color. They are uniform in size, regularly distributed and are 

 about 0.5 furrow's width in diameter. 



We find no striae on our specimen on close examination. Schiitt figures 15 across the ventral 

 face, following the torsion of the body and sparingly beaded. Both Schiitt's specimen and our 

 own were enclosed in a large, spheroidal, double-contoured, hyaline cyst, 1.5 length of the body 

 in diameter. 



Dimensions. — Length, 60-84/^; transdiameter, 35-50/^; axes of nucleus, 32/* 

 and 21/*, 27/* and 20/*. The second figure in each case is of Schiitt's specimen. 



Activities. — Our specimen was first seen at 4 p.m. in a plankton catch taken 

 at 8 A.M. At 6 P.M. it was still active, circling within the cyst incessantly /rilJiouf 

 a single observed rotation, in anticlockwise circles. The transverse flagellum 

 was active during this circling. 



OccuKRENCE. — This ^\as first observed July 5, 1917, in a haul G miles off 

 La Jolla. California, from 80 meters to the surface and in a surface temper- 

 ature of 21 ?9 C. It was also observed in hauls made July 23, 6 miles offshore, 

 from 80 meters to the surface, on Jttly 27, 4 miles offshore, from 80 meters, 

 and on August 20, 0.75 mile o ff shoi-e in temperatures ranging from 20?8 C to 

 21 ?9 C. 



