328 MEMOIRS OF THE UNIVEESITY OF CALIFORNIA 



Biological Station at La Jolla and in the hauls made 4 and 6 miles offshore 

 f]*om 80 meters to the surface. 



It was firvSt figured by Schiitt (1895) from the material of the Plankton 

 Expedition, presumaljly from the Bay of Naples or the Atlantic. 



Syxoxymy. — Originally figured by Schiitt (1895, pi. 21, fig. 65) as Gymno- 

 di Ilium spiraJe var. pinguis, but later assigned to Spirodiiuum by Lenuiiermami 

 (1899). Specific rather than varietal status for this fonn is indicated by its 

 stouter fusiform shape, lack of torsion of the body, and heavy peripheral layer 

 of rodlets, all of which characters distinguish it from G. spirale. 



Co:\[PABisoxs. — This species is close to G. ovoideum in size and proportions, 

 ibut is green instead of yellow and has less torsion, displacement of gii-dle and 

 as'STimietrv. 



Gyrodinium postmaculatum sp. nov. 



Plate 6, figure 64 : plate 8, figure 91 ; text figure DD, 20 



Diagnosis. — A medimn sized species with obovoidal body, its length 1.86 

 transdiameters ; girdle a descending left spiral, displaced 0.66 transdiameter ; 

 sulcus extending from apex to antapex ; surface striate with liroken lines ; color, 

 amaranth purple. Length, 86/*. Pacific off La Jolla, California, July, August. 



Descriptiox. — The body is stout obovoidal to ellipsoidal in outline, rounded anteriorly, more 

 tapering posteriorly, circular in cross-section, its length 1.86 transdiameters at the widest part, 

 which is in the upper third of the hypocone. The hypocone exceeds the epicone in size, its length 

 being greater by 0.09 of its own length. The epicone is elongate hemispherical anteriorly, its 

 sides subparallel posteriorly, with the apex sometimes projecting sliglitly above the surrounding 

 surface. It has a length on the left and right sides of 0.2.5 and 0.63 respectively of the total 

 length of the body. The hypocone is rounded anteriorly, tapering to a slender point posteriorly. 

 It has a length on the left and right sides of 0.7 and 0.36 respectively of the total length of the 

 body. Its transdiameter anteriorly is greater than that of the epicone and its sides are more 

 convex, and the antapex may be metabolic. It often forms a more or less acute antapical point. 



The girdle is premedian for most of its course. Its proximal end joins the sulcus at a distance 

 from the apex of 0.25 and its distal end 0.63 respectively of the total length of the body. Its 

 course about the body for the first 0.5 of its length is in a nearly transverse direction, beyond 

 which it turns posteriorly at a gradually steepening angle which becomes about 40° with the 

 longitudinal plane of the body, at its junction with the girdle, with a displacement of 0.66 

 transdiameter. The furrow is narrow, having a width of about 0.02 transdiameter, and is deeply 

 impressed with smoothly rounded edges. The sulcus reaches the apex where it forms a slightly 

 enlarged, rounded pit, with its proximal border sliglitly raised above the surrounding surface. 

 It extends posteriorly as a deep trough in a nearly straight line to within a short distance of the 

 antapex, where it fades out. Its width is variable, narrowed anteriorly, enlarging at the anterior 

 pore to about twice the width of the girdle, and becoming narrower again beyond the posterior 

 pore. The anterior flagellar pore opens at the proximal junction of the girdle and sulcus, the 

 posterior pore a short distance beyond the distal junction. 



The nucleus is a large, spheroidal body filled with coarse, moniliform chromatin strands. It 

 is slightly premedian in position, lying dorsad to the anterior flagellar pore. Its axis is about 

 0.52 transdiameter in length. 



