FAMILY GONYAULACACEAE 



51 



cur on many plates. Thus any diagnosis of the plate pat- 

 tern based on the pattern of ridges would be erroneous. 

 Careful dissection is necessary to insure a correct plate 

 formula. The third apical and the second anterior inter- 

 calary are particularly difficult to demonstrate. The 

 second apical bears two ridges removed from the edges; 

 the first anterior intercalary has three (fig. 63 A). 



The antapical spine is massive, solid, and conical, 

 terminating the hypotheca and borne by the antapical 

 plate. It Is 4.1 (2.4-4.5) girdle widths long and from 1 

 to 2 girdle widths in diameter at base. It is covered 

 with the same fine areolation as that of the body and is 

 marked with ridges running longitudinally. 



Variation . Gonyaulax fusiformis shows considera- 

 ble variation in size and in length of antapical spine, but 

 other characters are comparatively constant. Length of 

 body varies from 67 to 98 microns; length of antapical 

 spine from 12 to 23 microns or from 2.4 to 4.5 girdle 

 widths. Body shape very constant except that width at 

 girdle shows a tendency to vary; the_l/d ratio varies 

 from 1.68 to 1.98. Sometimes the "sulcal spine" is 

 double, and one specimen was found without this spine. 

 The surface markings show a high degree of constancy, 

 being always a very delicate areolation with scattered 

 large pores. The right sulcal list may end at sulcal 

 spine or may continue beyond to antapical end of sulcus. 



Comparisons . Although the plate pattern of G. fusi - 

 formis is ftmdamentally similar to that of G. pacifica , it 

 differs somewhat from that of the latter species. Its ma- 

 jor plate pattern is composed of the same number of 

 plates as that in G. p acifica, but the arrangement of its 

 plates differs from that in G. p acifica in some respects. 

 Its first apical does not reach the girdle as it does in G. 

 pacifica , but extends only to the anterior sulcal plate. 

 Its third apical is much smaller, so that its second an- 

 terior intercalary touches the first intercalary, which is 

 not the case in G. p acifica . The apical process of ap31s 

 not represented in G. p acifica . 



In regard to the ventral area, the arrangement of the 

 plates in G. fusiformis is rather similar to that in G. 

 pacifica , but there is one less plate in the former spe- 

 cies; the posterior accessory is lacking. In G. pacifica 

 the Intercalary plate is next to the largest of the sulcal 

 complex, whereas in G. fusiformis it is the smallest. 

 Its position, however, on the right of the sulcus just an- 

 terior to the posterior plate and not touching the flagel- 

 lar pore, is the same in the two forms. The extra sul- 

 cal plate in G. p acifica, the posterior accessory, is pos- 

 terior to the flagellar pore. Its anterior end forms the 

 posterior end of the pore. It has probably been formed 

 by the splitting off from its neighbor to the left, the left 

 sulcal plate. Thus, tlie left and posterior accessory sul- 

 cal plates in G. pacifica would be homologous with the 

 left sulcal plate in G. fusiformis ; this latter plate has an 

 arm extending along the left side of the pore to pol, 

 probably homologous with the anterior part of the left 

 sulcal plate in G. p acifica . 



Gonyaulax fusiforiais shows some relationship to 

 Spiraulax kofoldli and in some respects it is intermedi- 

 ate between Spiraulax and Gonyaulax . It agrees with 

 Spiraulax in that the second anterior intercalary plate 

 touches the first (which in Spiraulax. however, is the 

 third apical). It also agrees in the number of the sulcal 

 plates, viz., six. The general arrangement of the sulcal 

 plates in the two species is the same although there are 

 two important differences in the details of the arrange- 

 ment: First, in Spiraulax the left sulcal plate does not 



have an arm extending along the side of the flagellar 

 pore, so that the entire left side of the pore is formed 

 by the first postcingular plate; the left sulcal plate marks 

 only the posterior edge of the pore. Secondly, the rela- 

 tive sizes of the plates differ in such a way that in Spir - 

 aulax the right sulcal plate has been squeezed out from 

 contact with the pore, so that the right side of the pore 

 is formed chiefly by the right accessory sulcal plate and 

 to a small extent by the notch of the anterior plate. So 

 far as the sulcus is concerned, it may be concluded that 

 G. fusiformis is more closely related to G. p acifica than 

 to Spiraulax . The agreement with Spiraulax in the num- 

 ber of plates is outweighed by the difference in the pat- 

 tern of the sulcal plates. Only the splitting of one plate 

 in G. pacifica is sufficient to show good agreement with 

 the sulcal plates of G. fusiformis, whereas considerable 

 adjustment of plates surrounding the pore would be nec- 

 essary to show agreement with Spiraulax . 



Differences in the epithecal plate pattern emphasize 

 the distant relationship of these two forms. In Spiraulax 

 the plate which is homologous with the first anterior in- 

 tercalary in Gonyaulax fusiformis is an apical. Thus in 

 Spiraulax there are four aplcals and only one anterior 

 intercalary, whereas in G. fusitormis there are only 

 three aplcals and two intercalaries. In Spiraulax the 

 first apical does not extend either to the girdle or to the 

 anterior sulcal plate, but terminates at the anterior 

 margin of the first precingular, so that the anterior In- 

 tercalary extends over and touches the first precingular. 

 Kofoid (1911b) stressed this point in creating the genus 

 Spiraulax . The ventral epithecal pore so characteristic 

 of the genus Gonyaulax is absent in Spiraulax . 



There is a superficial resemblance between G. fusi - 

 formis and Spiraulax in general body shape, so that 

 when a specimen of the former species is viewed under 

 the low power of the microscope it may be confused with 

 a species of Spiraulax . Under the high power, however, 

 a glance at the surface of the plates is sufficient to dis- 

 tinguish these two forms without any analysis of the plate 

 pattern. Spiraulax is coarsely reticulate or with round- 

 ed pits, without apparent pores. Gonyaulax fusiformis 

 is very finely areolate with a few large pores scattered 

 over the plates. The prominent sulcal spine will dis- 

 tinguish this species from Spiraulax. although its ab- 

 sence is not a positive identification of Spiraulax . 



Blstorical . It Is possible that Murray andWhitting's 

 Gonyaulax j oUlffel (1899, p. 324, pi. 28, fig. la, b) was 

 based on an aberrant specimen of G. fusiformis (see p. 

 54). The plate pattern is so poorly figured by these 

 authors that definite identification is not possible. The 

 presence of a left sulcal spine and the general body 

 shape suggest, however, that Murray and Whittlng s form 

 is not specifically identical with our material. For this 

 reason and in order to avoid confusion in the literature, 

 it was deemed advisable to give our species a new name 

 and to retain the name Gonyaulax j olllffel for Murray 

 and Whltting's species. Kofoid s Spiraulax is separate 

 from each of these (see p. 52). 



Gonyaulax fusiformis was figured by Pavillard(lQSl, 

 pi. 2, fig. 3) under the caption Gonyaulax birostrls Stein. 

 Although the plate pattern is not indicated, this form Is 

 easily Identifiable with the present species by its char- 

 acteristic body shape and antapical spine. The spedas 

 differs from G. birostrls Stein in body shape and pUto 

 pattern. 



Distribution . Pavillard (1931) reported this spe- 

 cies from the tropical Atlantic. 



