250 TJmversitij of California Publications in Zoology. [Vol. 8 



The two ends are both sometimes curved posteriorly and the distal end 

 declines steadily in a long slope from the right side of the body. The 

 furrow is relatively narrow, very deeply impressed with salient ridges 

 bearing low, abundantly ribbed fins of 0.5 girdle width in height. The 

 anterior plate {ant. pi., pi. 14, fig. 32) of the ventral area indents the 

 epitheca nearly half way to the apex. The ventral area or longitudinal 

 furrow is much compressed laterally between the ends of the girdle where 

 it malves an angle of 25° with the major axis. The salient right mid- 

 ventral region with the distal end of the furrow crowds the furrow to the 

 left and (pi. 17, fig. 45) overhangs it. Posteriorly it flares very abruptly 

 to the right side to 3 girdle widths at the postmargin. 



The plate formula is 3', 0", 6", 6, 6'", IP, 1"". Apical I' is a short plate 

 0.2 transdiameters in length and 0.5 to 0.8 girdle width across bearing at 

 its apex the elongated elliptical closing platelet (cl. pi., pi. 14, fig. 32). 

 Apical 3' bears in its median margin less than a girdle width below the 

 apex the conspicuous ventral pore (v. po.). Precingular 6" is quadrangu- 

 lar. Fostcingular 1'" relatively broad, 1 to 2 girdle widths across; pos- 

 terior intercalary very wide; antapical 1"" rather widely and deeply 

 invaded by posterior plate of ventral area. Ventral area with long, slender 

 anterior plate (ant. pi., pi. 14, fig. 32) nearly 3 girdle widths in length, 

 partially crossed by the anterior girdle ridge, with a shallow notch at its 

 postmargin for flagellar pore. Intermediate plates obscured. Posterior 

 plate beginning about two girdle widths behind the distal end of girdle 

 and flaring rapidly and principally to the right side, expanding from one 

 girdle width anteriorly to three at the postmargin. 



The surface is very characteristically marked with a light tracer_y of 

 delicate meshwork made up predominantly of longitudinal or semi- 

 detached vermiculate elements with which transverse or irregular bars 

 form an incomplete mesh. In some specimens the mesh work is pre- 

 dominantly polygonal, especially on the hypotheca and near sutures. On 

 others the longitudinal pattern predominates especially on pre- and 

 postcingular plates and along suture lines (pi. 17, figs. 45, 46). The low 

 fin on the girdle lists is very abundantly ribbed as are also the low 

 fins on plates 1'", 6'", and IP which overhang the longitudinal furrow. 

 The low fin between the two antapical spines is likewise minutely and 

 abundantly ribbed. In fact the fins throughout are all low and abun- 

 dantly ribbed, the distance between the thickenings in their substance 

 corresponding remarkably well with the diameter of the polygonal 

 meshwork upon the shell, suggesting the action of a similar physical 

 factor determining both. The only fin showing an unusual development 

 is the one on plate 1'". In most species of Gonyaulax no fin appears 

 here or at the most it is a very low list. In this species it almost com- 

 pletely covers over the furrow. In one specimen (pi. 17. fig. 46) the girdle 

 lists are lacking and there is no fin on the postmargin between the anta- 

 pical spines. The two antapical spines are short (0.6 girdle width), stout, 

 and finned on both sides, or entirely lacking fins. 



The pores are sparingly distributed, in rows along sutures, in the 

 girdle where the two rows are joined by vertical ribs as in G. scrippsae, 



