310 University of California Publications. [Zoology 



The transverse furrow is impressed, with ribbed membranous 

 lists. It has strong proximal arch and little distal displacement. 



Thecal wall with three mid-dorsal epithecal plates, sutures 

 with broad bands of intercalary striae, surface areolated, with 

 nodal pores. Plasma reddish. 



Length, 80-90|U, ; transdiameter, 67-80/x. 



Common in neritic plankton in summer off San Diego. 



Peridinium minutum, sp. no v. 



PI. 31, figs. 42-4.5. 



A minute species of globular form with a low apical horn and 

 no antapical extension. Two dorsal intercalary plates instead of 

 three. 



The body is spherical, without ventral flattening or excava- 

 tion. The epitheca slightly exceeds the hypotheca and ends in an 

 abruptly differentiated stout apical horn whose diameter is 0.7 

 and height 0.5 of the width of the transverse furrow. The hypo- 

 theca plus the girdle is about equal to the epitheca. It has no 

 antapical horns or spines. The girdle is horizontal and not dis- 

 placed. The lists of the transverse furrow are low hyaline fins. 

 The longitudinal furrow expands posteriorly and is bordered by 

 membranous lists with two distal ribs and one in the highest part 

 of the left list. Thecal wall hyaline, porulate, without reticvila- 

 tions (in individuals thus far examined). Sutures marked by 

 well defined lines and short intercalary striae. 



Differs from P. glohnlus in the presence of the short apical, 

 the non-displaced girdle and its smaller size. 



Length, 23-43|U, ; transdiameter, 23-47;ti. 



Abundant in May in San Pedro Harbor. California. 



Peridinium multistriatum, sp. no v. 



PI. 30, figs. 40, 41. 



A medium-sized species without apical or antapical horns, 

 characterized by thick walls with exceedingly wide striated inter- 

 calary bands. 



The body is rotund, subpentagonal in face view. Its length 

 and transdiameter are about equal but exceed the dorso-ventral 

 diameter. The epitheca is slightly contracted to a low eminence 

 containing the slit-like apical pore and flares as it approaches the 



