KOFOID AND SWEZY: UNARMORED DINOPLAGELLATA 319 



The peripheral zone of cytoplasm is filled with short rodlets, presumably arranged at right 

 angles to the surface, as in other species, but these are not figured by Schiitt, who also omits oil 

 vacuoles in the cytoplasm. Color? 



Dimensions. — Length, 78^^ ; transdianieter, 30^ ; axes of nucleus, 23m and 17/^. 



Occurrence. — Figured by Seliiitt (1895) from material collected by the 

 Plankton Expedition, presumably from the Atlantic or from Bay of Naples. 



Synonymy. — This was figured by Schiitt (1895) as GijmnodinuDn spirale 

 var. mitra and changed by Lenmiermann (1899) to Spirodinium spirale var. 

 mitra. It lacks the characteristic striate surface of spirale, however, and is 

 also distinct from that species in its proportions ; hence it can hardly be regarded 

 as a variety of that species. We therefore propose for it specific rank under 

 Schiitt 's varietal name. 



Gyrodinium obtusum (Schiitt) 



Plate 9, figure 103 ; text figure DD, 3 



Gymnoddnium spirale Bergh var. obtusa Schiitt (1895), pi. 22, fig. 70. 

 Spirodinium spirale var. ohtusum, Lemmermann (1899), p. 359. 

 8. spirale var. ohtusa, Schroder (1900), p. 13. 

 6. spirale var. oitusum, Lebour (1917&). 



Not Gymnodinium spirale var. ohtustim Dogiel (1906), pp. 38-43, pi. 2, figs. 50-56 (= 

 Gymnodinium hetcrostriatum nom. sp nov.). 



Diagnosis. — A meditun sized species with ellipsoidal subsymmetrical body, 

 its length 1.75 transdiameters; girdle a descending left spiral, displaced one 

 transdiameter ; sulcus extending from apex to antapex; surface finely striate 

 with broken striae; color, amber yellow. Length, 70^. Pacific off La JoUa, 

 California, Jidy; Atlantic, Gulf of Naples, Plymouth Sound, Englnd. 



Descru'tion. — The body is moderately broadly ellipsoidal with broad, rounded apices, widest 

 in the middle, its length 1.75 transdiameters at the widest part. A cross-section of the body is 

 nearly circular in outline. The hypocone is slightly larger than the epieone, though the posterior 

 deflection of a triangular portion of the epieone on the right ventral face gives it a greater 

 length than the hypocone. The epieone is convex conical (75°) with broad, blunt apex. It has 

 a length on the left and right sides of 0.22 and 0.80 respectively of the total length of the body. 

 The greatest increase in its length is made on the right side of the ventral face where the distal 

 border forms an angle of 45° with the longitudinal i)lane. The hypocone is somewhat broader 

 than the epieone with a broader, more blunt antapex. It has a length on the left and right sides 

 of the body of 0.18 and 0.72 respectively of the total length of the body. 



The girdle forms a steeply descending left spiral, displaced one transdiameter or 0.57 of the 

 total length of the body. Its proximal end joins the sulcus at a distance from the apex of 0.22 

 and its distal end 0.8 of the total length of the body. The first 0.5 transdiameter of its course is 

 in a transverse plane, the remainder a gradually steepening spiral which forms in the last 0.5 

 transdiameter, an angle of 45° with the longitudinal plane of the body. The furi'ow lia.s a width 

 of about 0.06 ti'ansdiamcter and is deeply impressed, its concavity undercutting the anterior 

 border and sloping gradually out to the i)osterior one. The sulcus extends from the apex to the 

 antapex in a nearly straight line. The trough is narrower than the girdle, shallow on the epicene, 



