KOFOID AND SWEZY: UNARMORED DINOPLAGELLATA 439 



Co:MrARisoxs. — Pouclwtia alha is' the least differentiated member of the 

 subgenus Pouchetin. Its primitive stage of development is indicated l)y the 

 very slight coloration and its location in the yellow-green part of the spectrum, 

 by the slight torsion of the sidcus and relatively small amount of displacement 

 of the gii'dlc. The intercingular region is equivalent to that found in the genus 

 G ij rod i Ilium. The ocellus is also in the diffuse stage with little evidence of 

 functional and structural integration. The two segments of the lens are not 

 fused, the pigment mass is small in amount, scattered in amoeboid processes 

 away from the lens, is not applied closely to any large area of the lenses and 

 contains no red core. Neither the adjustment of lens and pigment nor the 

 location and direction of the axis of the ocellus are suggestive of fimctional 

 efficiency. In these particulars this species is most nearly approached by P. 

 pou'cheti (fig. PP, 4). 



Pouchetia atra sp. nov. 



Plate 11, figure 126; text figure PP, 5 



DiAGxosis. — Body ovoidal; length, 2 transdiameters ; girdle a descending 

 left spiral of 1.6 turns, displaced nearly 1 transdiameter; sulcus with apical 

 loop of 1.75 turns, its torsion 2 turns; ocellus posterior, concentrated; lens 

 elongate; black, amoelioid melanosome with red central core. Length, 64/^. 

 Pacific off La Jolla, California, Jtdy. 



Description. — The body is rather slenck'r, ovoidal with the widi^st diameter below the equa- 

 torial zone. It is deeply constricted by the girdle anil the sulcus. The epieone considerably 

 exceeds the hypocone. The length of the epicene above the anterior flagellar pore is 0.4, and 

 at its distal extremity 0.8.5 of the total length of the body. It contracts distally, its apex is 

 rounded, and its sides are deeply grooved by the sulcus which makes 1.75 turns around it. The 

 hypoeone is slightly broader than the epieone and has proximal and distal lengths of 0.6 and 

 0.15 respectively of the total length of the body. It is slightly a.symmetrical and more convex 

 anteriorly. The antapex is asymmetrically rounded, being longer at the right. The sulcus makes 

 but a shallow groove down the left face, ending at or near the antapex. There is no antapical 

 process and no sulcal notch. 



The junction of the sulcus and girdle is located 0.4 of the total length of the body from the 

 apex. It sweeps around the body in a descending left spiral as a deep trough with bulging, 

 overhanging borders, making 1.6 turns before its posterior junction with the sulcus 0.15 of Hie 

 total length from the antapex. The anterior flagellar pore opens at its anterior junction with 

 the sulcus and the posterior flagellar pore at its posterior junction. The transverse flagellum 

 traverses 0.8 of its length. 



The sulcus takes origin near the apex and forms a descending left sjiiral of 1.75 turns befoi-e 

 reaching the anterior flagellar pore, beyond which it makes a sweeping curve to the right, 

 descends to the posterior junction with the girdle and thence posteriorly in almost a straight 

 line to the antapex. Its narrow channel is more deeply embedded anteriorly and on the left 

 face of the epieone than it is elsewhere, and especially toward the antapex. 



The ocellus is relatively large and is situated at the extreme posterior end. It is at the left 

 of and behind the sulcus, directed obli(|iu'ly anterosinistrally about 45° from the main axis. 

 The lens is of the imperfectly concentrated type and shows a marked tendency toward the 



