1911] Kofoid: On Sjnraulax. 297 



lax. Apical 1' does not in this species extend posteriorly between pre- 

 cingulars 1" and 6" as iu species of the genus Goiiyaulax, but terminates 

 obscurely some distance above the indenting ventral area. The right 

 intercalary i" is not found in the subgenus Fusigonyaulax, which con- 

 tains the species of Gonyaulax most resembling S. jolliffei. This is, in 

 Spiraulax, a large well-developed plate. It was overlooked by Murray 

 and Whitting (1899) but appears in Entz's (1905) figure. There are 

 six preeingulars, of which 1" is the longest, S" and 4" (middorsals) are 

 smallest, and 6" is quadrilateral and relatively very large, its size and 

 that of 1" being correlated with the spreading equatorial region. Of 

 the six posteingulars 1'" is very small and narrow, with a reticulate lip 

 overhanging the left margin of the ventral area. By reason of the 

 pressure of the left intercalary li>, the adjacent postcingular £'" is much 

 shorter than the other members of this series. The single antapical 

 1"", is conical in contour with a slight constriction midway of its length. 

 It bears on its distal end a short (1.5 girdle widths) stout, semi-hyaline, 

 solid, median spine. The girdle plates are six in number with sutures 

 {g. s.) as shown in the diagrams (pi. 19, figs. 1, 2). 



The ventral area (pi. 3 9, fig. 5) has a small anterior plate, and an 

 elongated posterior one (post. pi.). The intermediate plates are hidden 

 in the narrow furrow. 



The surface of the theca is variously marked. In thick-walled indi- 

 viduals the surface is deeply and regularly pitted with crowded, coarse, 

 circular pits with minute pores at the bottom and the girdle lists are 

 heavily and regularly ribbed. In thin-walled individuals both inner and 

 outer surfaces are faintly reticulate with subregular rounded polygons, 

 each with a minute pore in the center and the girdle lists are not ribbed. 

 In some cases the pits and reticulations are less regular and not all of the 

 pits bear pores. The single large pore of the ventral apical region so 

 conspicuous in species of the genus Gonyaulax is not found in S. jolliffei. 

 A peculiar round opening (op.) in the margin of the suture at the lower 

 median corner of apical plate 1' is visible on parting the plates. Low, 

 sparsely ribbed, hyaline lists which increase in height distally guard 

 either side of the ventral area, except in the distal region. The anta- 

 pical spine is a thickened symmetrical terminal extension of the anta- 

 pical plate, whose whole surface may be faintly areolated, but in some 

 cases is structureless and hyaline. Intercalary bands along the other- 

 wise unornamented sutures are sometimes to be seen. 



Cell contents dense, chromatophores dark yellow. Contents fre- 

 quently escape through the parted apicals. Empty thecae often abund- 

 ant in the plankton. 



Dimensions: Length, 132/*; transdiameter, 92|U,; dorso-ven- 

 tral, 75ju, ; width of furrow, o/x. 



Variation : San Diego material is more angular and much 

 less rotund than the specimen figured by Murray and Whitting. 

 The surface varies greatly in thickness of the reticulations and 



