52 



STUDIES IN THE MORPHOLOGY, TAXONOMY, AND ECOLOGY OF THE PERIDINIALES 



In the Carnegie collection G. fusiformis was found 

 at 19 stations: 2 in the Atlantic and 17 in the Pacific. 

 There are 33 records of occurrence, all rare. The spe- 

 cies occurred about equally at the three depths, with 12 

 records for the surface, 12 for 50 meters, and 9 for 100 

 meters. There are 21 pump records and 12 net records. 



The species was closely limited to the tropics. In 

 the Atlantic it did not occur north of 30° north. In the 

 Pacific it was not found north of 29° north or south of 

 16° south. No center of abundance was indicated. The 

 17 record stations in the Pacific were rather irregular- 

 ly scattered and showed no correlation with geographic 

 location or with dynamic conditions (fig. 61). 



The sxirface temperatures at the stations where the 

 species occurred at any depth varied from 22° 7 to 

 28°.7 C. The hydrographic conditions in situ were as 

 follows: temperature, 18°.7 to 28°.7 C; salinity, 34.2 

 to 37.0 o/oo; pH, 8.16 to 8.39; phosphate, 3 to 40 mg 

 P04/m3. 



This is obviously a rare tropical species restricted 

 to warm water. It is remarkable that it was found more 

 often in the nutrient-poor water. Of the 33 records of 

 occurrence, all but 7 were in water with a phosphate 

 content less than 10 mg P04/m3. Type locality: Car - 

 negie station 18. 



Genus ACANTHOGONYAULAX (Kofoid) Graham 



Diagnosis . Body angular, with prominent lists and 

 brush-formed hypothecal spines simulating Ceratocorys . 

 Girdle premedian. Plate pattern: apical platelet, 3ap, 

 9pr, 6g, 7s, 6po, Ip, lant. Ventral epithecal pore on 

 first apical plate. One species. Marine. 



Type species . Acanthogonyaulax spinifera (Murray 

 and Whitting) Graham. 



Historical . Acanthogonyaulax was proposed as a 

 subgenus of Gonyatilax by Kofoid (1910) to include Mur- 

 ray and Whitting s (1899) Ceratocorys spinifera (see 

 below, pp. 51-52). This subgenus is here raised to the 

 rank of genus. 



Comparisons . Acanthogonyaulax has a superficial 

 resemblance to Ceratocorys, particularly to C. horrida . 

 The hypotheca of Acanthogonyaulax resembles that of C. 

 horrida in the great development of antapical brush 

 spines and in the intervening lists. The epitheca, on the 

 other hand, is prolonged into a short tubular horn, 

 whereas in Ceratocorys the epitheca is low dome-shaped. 



A more fundamental resemblance between these two 

 genera is expressed by the similar number and pattern 

 of the major hypothecal plates. There is a disparity in 

 the size of some of these plates, however. 



The posterior intercalary is much more extensive, 

 and the first postcingular is gomewhat larger in Acan - 

 thogonyaulax than in Ceratocorys . The second postcin- 

 g\ilar, on the other hand. Is a small ventral plate in 

 Ceratocorys . whereas In Acanthogonyaulax it is large, 

 equal in size to the postcingulars of the lateral and dor- 

 sal sides. 



The epitheca of Acanthogonyaulax differs markedly 

 from that of Ceratocorys, not only In shape but also in 

 the number and the pattern of the plates. The number 

 of precingular plates in Ceratocorys Is five; in Acan - 

 thogonyaulax it is nine. The major part of the epitheca 

 In Ceratocorys is composed of four precingular plates, 

 whereas in Acanthogonyaulax six of the precingular 

 plates constitute most of the epitheca. The small first 



precingular plate in Ceratocorys is represented in 

 Acanthogonyaulax by three minute precingulars. The 

 apical region in Ceratocorys is composed of four plates: 

 two apicals and two inter calaries; in Acanthogonyaulax 

 there are three plates in this region, all apicals. 



A study of the sulcal complex of these two genera 

 shows even less relationship between them than does a 

 comparison of the epithecal plates. There are seven 

 plates in the ventral area of Acanthogonyaulax , and only 

 five in Ceratocorys . Acanthogonyaulax is unique in that 

 the anterior sulcal plate is removed from the flagellar 

 pore. In Ceratocorys the posterior part of the ventral 

 area never flares out into a prominent part of the ven- 

 tral aspect as it does in Acanthogonyaulax . This feature, 

 on the other hand, is characteristic of Gonyaulax . 



Acanthogonyaulax is more closely related to Gon - 

 yaulax than to Ceratocorys . The hypotheca has the same 

 number of plates in the two genera, although the arrange- 

 ment is somewhat different. In Gonyaulax the first post- 

 cingular is much smaller and the posterior intercalary 

 is much longer and narrower than in Acanthogonyaulax . 

 The antapical plate in Gonyaulax is more restricted. 



It is more difficult to compare the epithecal and 

 sulcal plates of Acanthogonyaulax with those of Gonyau - 

 lax than with those of Ceratocorys because so little crit- 

 ical work has been done on Gonyaxilax . For that reason 

 the present discussion is based on only two species of 

 Gonyaulax ; G. pacifica and G. fusiformis . As stated 

 above (p. 46), the present concept of the genus Gonyau - 

 lax is probably too broad. 



The first apical plate in Acanthogonyaulax does not 

 extend to the girdle or to the ventral area; in Gonyaulax 

 it extends to the girdle. The number of precingular 

 plates is six in Gonyaulax, nine in Acanthogonyaulax . 

 The extra three precingulars in the latter genus are the 

 three minute ventral ones, the first, second, and third. 

 It is possible that the first two represent the anterior 

 part of the anterior sulcal plate of Gonyaulax," in which 

 case the anterior part not only has separated from the 

 posterior part but also has spUt longitudinally. The 

 third precingular could, then, represent the lower part 

 of the first antapical of Gonyaulax . There is much great- 

 er difficulty in homologizing the sulcal plates proper of 

 these two genera, in spite of the fact that the total nimi- 

 ber of plates may be the same. The flagellar pore does 

 not bear the same relation to the various plates in the 

 two genera (see fig. 1). In Acanthogonyaulax the anteri- 

 or sulcal plate is removed from the pore, whereas in 

 Gonyaulax it forms its anterior edge. In Acanthogonyau - 

 lax the pore is bordered by four plates, two anterior, 

 two posterior; in Gonyaulax it is bounded by five plates, 

 only one of which is anterior, one is posterior, the rest 

 lateral. The greatest resemblance in these areas seems 

 to be that the posterior plate in each case is the largest. 

 Their differente in shape, however. Is extreme. In 

 Gonyaulax it is subelliptical; in Acanthogonyaulax , sub- 

 triangular with two widespread limbs. 



On the basis of the differences In the epithecal and 

 sulcal plate patterns, we are forced to conclude that 

 Ac anthogonyaulax Is only remotely related to the species 

 of Gonyaulax included in this report. If further investi- 

 gations show that other species, now allocated to Gon - 

 yaulax , are similar in pattern to G. pacifica and G. fusi - 

 formis , then we may conclude that Acanthogonyaulax 

 and Gonyaulax not only are distinct genera but are sep- 

 arated by a divergent evolutionary development of con- 

 siderable extent. 



