KOFOID AND SWEZY: UNARMOKED DINOFLAGELLATA 425 



Its siinple but eoneeutrated ocellus, its ueniatocysts, and its considerable 

 degree of torsion all mark it as one of the most specialized si)ecies of the genus 

 and family. 



Nematodinium partitum sp. nov. 



Plate 6, figure 68 ; text figures P, 2 ; MM ; NN, 4 



DiAGXosis. — A medium sized species, oA'oidal, length 1.7 transdiameters, 

 girdle a descending left spiral of 1.25 turns, displaced 0.8 transdiameter, sulcus 

 with both apical and antapical loops, its torsion 1.75 turns, ocellus of distributed 

 type with numerous spherical lenses and diffuse black melanosome, situated 

 far posteriorly; numerous nematocysts radiating from center. Length, 91/^. 

 Pacific off La Jolla, California, June, July. 



Description. — The body is ovoidal with the broadest diameter slightly anterior to the equa- 

 torial region. The epicone and hypoeone are subequal. The epicone is broadly rounded at the 

 apex with a length above the anterior flagellar pore of 0.3 and distally on the right of the sulcus 

 of O.S of the total length of the body. The hypoeone is abruptly truncate at the right, is longer 

 on the left side and broadly rounded there. It is traversed dorsally by the tip of the sulcus 

 which sweeps around antapex in 0.66 of a turn and marks off a small, rounded terminal lobe. 



The junction of the girdle and sulcus occurs at a point 0.3 of the total length from the apex. 

 It curves around the body in a semicircle before taking a posterior direction, making 1.25 turns 

 before meeting the sulcus at a point 0.13 of the total length from the antapex. It lies in a deep 

 depression anteriorly, but less so distally. It is everywhere deeply impressed with overarching 

 lips. The anterior flagellar pore opens at its anterior junction with the sulcus and the posterior 

 pore just beyond its posterior junction. The transverse flagellum traverses 0.25 the total length 

 of the girdle. 



The sulcus invades the epicone in a broad curve, sweeping around nearly 0.75 of a turn in 

 a deep trough which fades out distally. Below the anterior flagellar pore it describes 0.25 

 circumference in reaching its posterior junction with the girdle, beyond which it sweeps around 

 the dorsal side of tlie hypoeone in nearly a complete (0.75) turn of the descending spiral. On 

 the dorsal side at this point the hypoeone forms a deep, overhanging shelf on the proximal 

 bordei' of the sulcus, its distal border showing no percejitible protrusion. 



The ocellus is situated below the distal end of the girdle and at the left of the sulcus and the 

 posterior flagellar pore and extends in a dorsoventral direction. Its lengtli is about 0.3 trans- 

 diameter. It consists of a distributed lens and a black amoel)oid melanosome. The lens is 

 composed of about fifteen to twenty greenish yellow, spheroidal, hyaline bodies packed in thi'ee 

 layers, embedding the bases of the lens, and extending in long granular strands around tlieni is 

 the black pigment of the melanosome. Numerous black granules are scattered in rows along 

 the borders of the girdle and the sulcus, especially posteriorly. 



The nucleus is large, ellipsoidal, spherical, or pyriform and elongated posteriorly. It is 

 situated near and anterior to the antei'ior flagellar pore. Fine chromatin .strands traverse it, 

 some in spiral directions. Its major and minor axes are 0.56 and 0.7 transtliameter in length 

 respectively. 



No pusules were observed. The cytoplasm is clear and very finely graiuilar. A lunuber of 

 miiuite oil glol)ules were present at the antei'ior end and a greater number in the posterior i)art. 

 Scattered through the cytoplasm are numerous (l;>-20) nematocysts, greenish yellow in color. 

 These are considerably smaller than those found in N. armatum, having a length of 5-.S/i and a 

 width of 2-3/n. The majority take, in general, an antero]iosterior direction. They are arranged 

 roughly in three groups: one in the anterior part, one near the central region, and tlie third 



