FAMILY GONYAULACACEAE 



55 



Spiraulax kofoidii new name 

 (Figure 66) 



Spiraulax j olliffei Kofoid, 1911b, pp. 296-298, pi. 19, 

 figs. 1-5. Forti. 1922, p. 82, pi. 6, fig. 71. not 

 Gonyaulax j olliffei Murray and Whitting, 1899, p. 

 324, pi. 28, fig. la, b. 



Dimensions . Length of body (IJ, excluding antapi- 

 cal spine, 123 (101-160) microns. Diameter at girdle 

 (d) 79 (71-105) microns. Length of antapical spine 10 

 (0-18) microns. Width of girdle 5 to 6 microns. Twenty- 

 nine specimens were measured. 



Shape . Body broadly fusiform. The j/d ratio is 

 1.54 (1.40-1.77). Epitheca prolonged as an apical horn 

 extending 0.75 transdiameter from proximal end of gir- 

 dle. Hypotheca also extends as a horn but is shorter 

 than epitheca; length 0.46 transdiameter, measured 

 from distal end of girdle. Antapical horn terminates in 

 a stout spine about 2.5 girdle widths long; in strongly 

 sculptured specimens sometimes so heavy thi^t it ap- 

 pears as a continuation of the body proper. Kofoid' s 

 (1911b, pi. 19) specimen does not show the spine al- 

 though he indicates it in his diagnosis. In ventral view 

 (fig. 660) epitheca usually somewhat concave on left side 

 but with prominent hump on right side, although Kofoid's 

 figure does not show much convexity on right side. Hy- 

 potheca has concavity on right side with hump on left 

 side. In apical view body almost circular except for 

 Indentation at sulcus, where girdle is depressed about 

 2 girdle widths (fig. 66D, E). Girdle approximately 

 equatorial, sinistral, displaced from 3 to 4 girdle 

 widths; deep excavation obscured by heavy sculpturing; 

 no overhang. 



Ventral area elongate, slightly sigmoid, narrow in 

 middle but expanded at both ends (fig. 66 A, G). It ex- 

 tends into epitheca about 2.5 girdle widths. Between 

 girdle ends it is extremely narrow but posteriorly it 

 flares out into an elliptical flat area almost 2.5 girdle 

 widths wide, then narrows somewhat to antapex. Flagel- 

 lar pore narrow, elongate, extending from posterior 

 margin of proximal end of girdle to anterior margin of 

 distal end. 



Plate pattern . First and fourth apicals ventral; 

 comparatively small. Second and third apicals large 

 and dorsal (fig. 66C, E, G). 



Apical plates separate easily and preserved speci- 

 mens are usually found with apicals parted. No apical 

 platelet found in our material, but this may be due to its 

 ready loss during the parting of the apicals. First api- 

 cal does not extend to girdle but terminates at anterior 

 edge of prl. Anterior intercalary large, lying between 

 ap4 and pr6 and part of pr5. First precingular large, 

 extending a quarter of the way around left side of body. 

 Other precingulars subequal in size, the third and 

 fourth being the smallest. 



The six girdle plates subequal in length except the 

 sixth, which is much longer than the rest. Positions of 

 sutures between girdle plates indicated by arrows in 

 figure 66E. The six postcingulars subequal in size ex- 

 cept the first, which is small and borders flagellar pore. 

 Posterior intercalary is broad, lies between pol to po3, 

 and antl, and borders middle third of left edge of ven- 

 tral area. Antapical plate large, forming distal part of 

 conical antapical horn. Posterior part of ventral area 

 set into its ventral face. 



Ventral area composed of six plates: a large pos- 

 terior plate, a medium-sized anterior plate, and four 



small intermediate plates (fig. 66A, B). Anterior plate 

 forms anterior margin of flagellar pore and extends into 

 epitheca almost halfway up side of anterior intercalary, 

 where it ends in a point. It has an arm which extends 

 posteriorly along anterior part of left edge of the pore. 

 The rest of right edge of the pore is formed by right ac- 

 cessory sulcal plate; the right sulcal plate barely touch- 

 es the pore. Left sulcal plate forms only posterior edge 

 of pore. Left edge of pore formed by first postcingular 

 plate. Intercalary sulcal plate lies between posterior 

 and right sulcal plates. The posterior sulcal plate 

 forms a large elliptical area on hypotheca. Most of the 

 sulcal plates are rotated on their long axes or are dis- 

 torted in the formation of the deep sulcus so that their 

 broadest aspects are not seen in ventral view. Figure 

 66B shows the sulcal plates in their broadest aspects. 



Thecal wall. All our specimens are thick-walled, 

 but Kofoid (1911b) found thin-walled individuals. Body 

 of thinner individuals covered with a definite reticula- 

 tion with rounded meshes; but in heavier specimens, 

 this type of differentiation gives way to a very thick wall 

 with fairly regularly spaced pits. Kofoid states that 

 these pits have minute pores in the bottom, but these 

 were not detected among the Carnegie specimens under 

 the oil immersion objective. Ventral epitheca! pore ab- 

 sent. Surface sculpturing weak or lacking along plate 

 sutures; sometimes there is here a zone of smooth the- 

 cal wall more than a girdle width wide. Ridges or lists 

 along body sutures absent except at dorsal sutures of 

 apical plates, where very small lists occur. Girdle 

 plates with two rows of polygons or pits. Posterior sul- 

 cal plate reticulate or pitted. Pits and pores occur on 

 anterior and intercalary sulcal plates. Left and right 

 sulcal plates bear only pores; right accessory sulcal 

 plate is entirely smooth. 



The anterior part of the first apical plate is bent 

 into a U-shaped trough with concavity facing inward (fig. 

 66E). In this manner the apex is formed almost entirely 

 by the first apical alone. When a specimen is viewed 

 ventrally, the sides of this trough appear as two dark 

 lines, so that the area between is light by contrast. 

 Kofoid interpreted this as a notch extending from the 

 apex and covered by a thin membrane, and suggested 

 its similarity to a structure in the first apical of Peri- 

 dinium . This is, however, an optical illusion which can 

 be dispelled by examining the separated apical plate in 

 apical view. The structure in Peridinium, moreover, 

 is quite different from this. In that genus there is a dis- 

 tinct linear plate, the ventral apical platelet, which lies 

 between the apex and the anterior end of the first apical 

 plate (see p. 16). 



All sutures, including those of girdle and ventral 

 area, formed as rabbet joints with underlapping mem- 

 branes as in Peridinium (see p. 10). The membranes 

 of the girdle plates do not underlap the body plates, but 

 lie against the cingular lists, which are attached to the 

 body plates (m, fig. 66F). Striated intercalary zones 

 were not found. 



Lists. Girdle lists about 1 girdle width wide; very 

 thick in thick-walled individuals, so that it is difficult 

 to distinguish them from body wall. In thinner individ- 

 uals, lists are strengthened by regularly spaced, stout 

 spines running out from body wall almost to edge of 

 lists. In heavier individuals, these spines may be 

 branched or form a reticulation. Sulcal Usts well de- 

 veloped. Right anterior sulcal list occurs along left 

 edge of precingular 6 and joins anterior girdle list. Left 



