NOTES ON DINOELAGELLATES. 27 



of A. kofoicli. In Part I of this report it was described as 

 A. sulcatum, Kofoid, but comparison with the description and 

 figures in his monograph, which has appeared since, show that 

 this identification was incorrect. 



This variety differs from A. kofoidi (see above) in the 

 larger and more flattened epicone, the deeply impressed and 

 undercut girdle and the thicker and rougher pellicle — also in its 

 paler and more greyish yellow colouration. 



[Both varieties of this species, together with A. eludens 

 (see above), are of especial interest in connection with the 

 phylogenetic position of the genus Amphidinium in the sub- 

 class Dinoflagellata. In the poor development of the epicone 

 in two of them, and in the presence of a pellicle covering the 

 body in all, they resemble the more primitive Adinif eridea , 

 while in other points they fall in more nearly with the generic 

 characters of Amphidinium. Possibly, then, the genus 

 Amphidinium may have branched off from the stem of the 

 Dinif eridea at a very early stage, close to the point of origin 

 of the Adiniferidea.] 



Amphidinium pellucidum, sp. no v. Occurring from time to 

 time in scrapings of sand containing coloured dinoflagellates — 

 especially from south end of beach. 



Description. Body almost symmetrical, broadly 

 elliptical and flattened dorsoventrally. Transverse axis 0*7 of 

 total length. 



Epicone much smaller than hypocone, almost equal in 

 width to greatest transdiameter, its length on the ventral side 

 being 26 of total length. Apex rounded and sometimes 

 slightly notched by a forward extension of the sulcus. 

 Hypocone broadly sack-shaped, rounded and notched poster- 

 iorly. Girdle deep, rising very little on dorsal side, broad at its 

 proximal and distal ends, which meet almost without displace- 

 ment. Transverse flagellum completely encircling the body. 

 Sulcus extending from apex to ant apex, very broad just 



