240 Universitij of Calif or)iia Puhlications in Zoology, [^ol. 8 



posterior intercalary, IP, is a rather large quadrangular plate and the 

 antapical 1"" , a subregular pentagonal plate indented at the midventral 

 angle by the rounded margin of the ventral area (pi. 12, fig. 19). 



The ventral area (pi. 17, fig. 43) indents the epitheca for half a girdle 

 width, the anterior plate being squarely truncate anteriorly and deeply 

 notched posteriorly by the flagellar pore (/?. po.). The posterior plate is 

 exceptionally large, extending anteriorly well toward the distal end of 

 the girdle. Three intermediate plates in addition to the hyaline scale of 

 the pore region have been isolated. 



The siirface is uniformly but not closely porulate with rather large 

 pores about which on a high focus a coarse reticulation may be seen. In 

 some cases the reticulum is finer than the porulation and some meshes 

 have no pores (pi. 14, fig. 31). In some cases no reticulum is visible or 

 merely a faint areolation. A regular line of pores follows each margin 

 of the girdle plates and in reticulate thecae the reticulum between these 

 resembles a columnar arcade. The ventral area in young specimens (pi. 

 17, fig. 43) is also porulate in its peripheral parts only. On the -v/hole, 

 the large size of the pores and feebly developed reticulum gives the 

 impression of a porulate rather than a reticulate type of theca in this 

 species. There are no free spines or lists other than those about the 

 girdle, which are low with stout denticulations rising from the basal 

 ridge. The theca of this species is rather fragile and is easily and quickly 

 shed, in fact ecdysis seems to be normal and frequent, judging by the 

 number of empty thecae and isolated plates found in the plankton wher- 

 ever the species is abundant. It also occurs very frequently in crowded 

 or moribund plankton collections. A thin pellicle surrounds the cell 

 body within the theca, the apical and precingular plates spread apart 

 along the longitudinal sutures, especially those in the sagittal plane, and 

 the Gymnodinium-Vike cell body escapes and presumably its thin pellicle 

 is differentiated into a new theca. 



The cell contents are very dark orange-brown and the chromatophores 

 are densely packed together. When present in great numbers, as they 

 often are, they give the sea a reddish color, and cause magnificent dis- 

 plays of phosphorescence at night. Oil droplets abound in the cytoplasm 

 and it gives off a rank odor upon decay. 



Dimensions: Length, 50 (43 to 54)ju,; transdiameter, 45.6 

 (37 to 53)/^; dorso-ventral diameter about the same; width of 

 girdle, 4 to 5/t. Ten individuals measured. 



Variation : There is considerable variation in size, in angu- 

 larity, in porulation, development of reticulum and girdle lists. 

 The displacement of the girdle varies from one to nearly two 

 girdle widths. The adjustment of apical plates to each other 

 also exhibits some irregularities in the lengths of the different 

 lines. Apical 4' varies considerably in size and one instance of 

 three anterior intercalaries has been recorded (pi. 14, fig. 28). 



