1912] Kofoid-Midiener : Dinosphaera palustris 27 



transdiameter, and thus displaying more plainly than usual its 

 constituent plates. The most anterior of these {ant. pi.) is 

 notched on its postmargin by the flagellar pore and is the 

 homologue of a similar plate in Gonyaulax in which also it abuts 

 anteriorly against apical 1'. The most posterior moiety is an 

 elongated plate [post, pi.) upon the left (of the body) side just 

 reaching to the antapical. Between the anterior and posterior 

 plates extends a series of four intermediate plates {int. pis.) The 

 first lies in the proximal end of the furrow adjacent to the flagel- 

 lar pore. The second is a thin scale on the posterior floor of 

 the pore region. The third is a narrow bar on the right side of 

 the pore and the fourth is a large, broadly exposed platelet lodged 

 in the distal end of the girdle. Pour intermediate plates have 

 been recognized by me (1911a) in various species of Gonyaulax, 

 where they usually lie in a more posterior location than in 

 Dinosphaera. The condensation of the hypotheea which has re- 

 sulted in the suppression of postcingular 1' " and posterior inter- 

 calary iP is also accompanied by a shoving forward of the inter- 

 mediate plates and their spreading out in the girdle region. 



The surface is devoid of all spines, lists or ornamentation of 

 any sort. The pores are few and mainly grouped about the vent- 

 ral area, nearly a dozen in all appearing on the ventral face. 

 Numerous small chromatophores and yellowish oil droplets are 

 present. 



Thus far reported only (Lemmermann, 1907) from ponds on 

 the moors of Brandenburg, in association with desmids, Perid- 

 inum wnboiiatum Stein, and P. achromaticum Levander. 



Dimensions. — Length, 27-34 fi ; transdiameter, 25-31 ;», ; width 

 of girdle, 4/*. 



Relationships. — Dinosphaera is one of the Ceratiinae related 

 to Gonyaulax by certain skeletal characters, such as the six pre- 

 cingulars, six girdle plates, and one antapical. In the presence 

 of but a single antapical it resembles also Amphidinium, Perid- 

 iniella, and Spiraulax. Other genera of this subfamily have two, 

 three, or four antapicals (see Kofoid and Michener, 1911). The 

 reduction of the postcingular from six to five plates and the 

 obliteration of the posterior intercalary might well be consequent 

 upon the skeletal concentration attendant upon the spheroidal 



