124 MEMOIRS OF THE UNIVERSITY OF CALIFORNIA 



Hemidinium ochraceum Levander 



Hemidinium ochraceus Levander (1900a), pp. 58, 61, 103, 104, fig. 2. 

 H. ochraceum, Lemmermann (1909), pp. 580, 618, figs. 14, 15. 



Diagnosis. — Body broadly ellipsoidal, its length 1.3 transdiameters ; epicoBe 

 about 0.25 of the hA7:)ocone ; girdle with 0.5 circuit, steeply descending on dorsal 

 face, sulcus not reaching postmargin; yellowish green to reddish brown; length, 

 23-33^. Fresh-water pools. Finland. 



Description. — This is as^nnmetrically and broadly ellipsoidal, widest at the middle, its length 

 1.3 transdiameters, slightly flattened dorsoventrally. The epicene, measured at the proximal end 

 of the girdle, is 0.25 of the total length. It is not separable from the hypocone on the right side. 

 The apex is flattened hemispherical in shape. The hypocone is three times as long as the epicone, 

 elongate hemispheroidal in shape with no sulcal notch in the postmargin. 



The girdle is incomplete, making a trifle less than 0.5 turn. From the proximal end it ascends 

 at an angle of 20° above the transverse plane to the left margin, where it turns abruptly poster- 

 iorly at an angle of 70° below the transverse plane, terminating in a narrow trough to the right 

 of the middorsal line a little below the equator. It has a net displacement of 0.35 and a total 

 displacement of 0.50 length of the body. The anterior lip is less protuberant than in H. nasuium, 

 and the posterior one is broadly rounded. The sulcus proceeds posteriorly from its junction with 

 the girdle about half way to the postmargin. Levander 's (1900a) interpretation of the girdle 

 and sulcus as a single furrow misconstrues the sulcus. The two flagella arise near each other at 

 the junction of girdle and sulcus. Lemmermann 's (1909) copy of Levander 's figure is in error 

 in uniting the two flagella at their bases. 



The nucleus is spheroidal, 0.33 transdiameter wide, and filled with chromatin grains. It is 

 located in the posterior part of the hypocone. The color is reddish brown anteriorly and yellowish 

 green elsewhere. Chromatophores not designated but presumably present. Cysts yellowish green 

 with reddish brown center, spheroidal. 



DiMEXSioxs. — Length, 26-33m; transdiameter, 23-26m. Cysts. 31m. 



OccT'EREXCE. — Descril)ed by Levander (1900rO as abundant in shallow rain- 

 water pools on rocks on the Skaren Islands, Finland, in association with H. 

 nasutum Stein. 



Comparisons. — Levander (1900r/) notes the presence on this species of a 

 thin "shell." If this is not merely a heavy pellicle, but a shell of the tyi^e found 

 in Glenodinium, this species, perhaps with H. nnsiitum, should be transferred 

 to the tliecate Peridinioidae. In any event, this species atfords, in this struc- 

 tural particular, an intermediate condition which tends to bridge over the gap 

 between the athecate G^^nnodinioidae and the thecate Peridinioidae. 



AMPHIDINIUM Claparede and Laehmann 



Text figure U 



Amphidinium Claparede and Laehmann (1858-61), p. 410, pi. 20, figs. 9-12. 

 Amphidinhim, Saville-Kent (1880-82), p. 461, pi. 25, figs. 44-46. 

 Amphidinium, Bergh (1882), pp. 693-695. 

 Amphidinium, Biitschli (1885), p. 1011, pi. 54. figs. 6, 7. 

 Amphidinium, Schiitt (1896), p. 4, fig. 4. 



