J ^11] Kofoid: The Genus Gonyaulax. 219 



{v. po., pi. 13, fig. 23) which in this species is quite large and often 

 elongated. The precingular plates are all large, except plate 6", which is 

 small and triangular in form. In a few cases observed its apex is 

 truncated but the length of the fourth side thus formed is not over a 

 girdle width. Postcingular plate 1'" is about 1 girdle width across and 

 3 to 5 in length. The posterior intercalary, IP, is an elongated pentagonal 

 plate to the left of the furrow. The single antapical, 1"", is relatively 

 small, and is not deeply indented by the ventral area. 



The anterior plate {aut. pi., pi. 13, fig. 23) of the ventral area is greatly 

 elongated in this species (4 girdle widths), expands anteriorly and is 

 deeply notched at its jiostmargin by the flagellar pore {ji. po.) The 

 intermediate plates {int. pis., pi. 13, fig. 21) are obscured in the depths of 

 the longitudinal furrow between girdle ends. The posterior plate (post, 

 pi.) is a rounded quadrilateral reaching anteriorly nearly to the level of 

 the distal end of the girdle. 



The surface of this species is most characteristic, its whole area 

 usually being reticulate with subregular polygonal mesh but not uniformly 

 so. Polygonal areas in each of the precingular and postcingular plates con- 

 tiguous on one side to the girdle are more heavily marked (pi. 16, fig. 40). 

 The more lightly marked margins bear the some relation to the plates that 

 intercalary bands do, and they are probably of this nature. These inter- 

 calary bands vary in width in different individuals and the contrasted 

 markings vary greatly in relative distinctness and in degree of develop- 

 ment in different individuals. In the more heavily marked forms (pi. 13, 

 fig. 24) the central reticulations are coarse and heavy and are less sharply 

 delimited from the lighter margins. In more lightly marked forms the 

 intercalary bands are very sharply marked off from the more densely 

 pitted or reticulate central regions. In some cases (pi. 16. fig. 40) the 

 intercalary bands are quite free from all but the faintest reticulations. 

 The pores are large, sparsely distributed over the more reticulated central 

 parts of the plates and located in the nodes of the mesh rather than in the 

 center of the enclosed areas. There are no girdle lists, but those of the 

 longitudinal furrow on plates 1'" and IP are heavily ribbed. The spines 

 on the antapex arise near the middle of the antapical plate and not from 

 the nodes of the sutures. They are usually two, occasionally but one, and 

 quite often three, the third being on the right side. The spines are usually 

 finned. The girdle is heavily reticulate except where crossed by inter- 

 calary bands. 



The contents are prone to escape through the parted apicals as in G. 

 polygramnia and G. polyedra. There is a centrally located ellijjsoidal 

 nucleus with moniliform chromatin network. The irregular chromato- 

 phores are of a yellowish brown color. The plasma is not especially 

 dense. 



Dimensions: Length (60) 75 to 100/*; transdiameter (45) 

 70 to 82/A ; width of girdle 4.5 to 5/a. The following measurements 

 apply to material from the San Diego region, and to figures 

 referable to the species. 



