54 



STUDIES IN THE MORPHOLOGY, TAXONOMY, ANT) ECOLOGY OF THE PERIDINIALES 



and tigured this species under the name Ceratocorys 

 spinifera . They not only erred in the generic allocation, 

 however, but they also confused the species with two 

 other species of Ceratocorys (Kofoid, 1910). Kofoid 

 (1910) realized the affinity of this species to the genus 

 Gonyaulax and placed it in this genus in his revision of 

 the genus Ceratocorys . No figures were given in this 

 report. Later, Kofoid (1911a) emphasized the differ- 

 ences between this and the other species of Gonyaulax 

 by placing it in a new subgenus, Acanthogonyaulax . 

 Since the specific name spinifera was preoccupied in 

 Gonyaulax , Kofoid proposed the new name ceratocoroides . 

 Kofoid (1911a, p. 202) described Acanthogonyaulax as 

 having six plates in the apical region instead of three. 

 He probably based his judgment on the drawings of 

 Murray and Whitting, in which the plate pattern of this 

 region is very obscure. 



On the basis of a detailed study of the skeletal anat- 

 omy of this species and of all the species of Ceratocorys , 

 as well as of two representatives of the genus Gonyau - 

 lax, Acanthogonyaulax is here raised to the rank of an 

 independent genus, related Iwth to Ceratocorys and to 

 Gonyaulax but separated from these genera by wide ev- 

 olutionary gaps. Since Murray and Whitting's specific 

 name spinifera is not preoccupied in Acanthogonyaula x, 

 it has priority and must be reinstated. 



Distribution . Acanthogonyaulax spinifera is an ex- 

 tremely rare tropical species. Murray and Whitting's 

 (1899) original material was from the Atlantic. Pavil- 

 lard (1931) found this species at one station off Spain in 

 1905. Apparently these are the only records of its oc- 

 currence up' to the present investigations. 



In the Carnegie collections the species was not 

 found in the Atlantic, but was collected at 22 stations in 

 the Pacific. These stations are widely distributed over 

 the tropical Pacific, grouped in the following manner: 

 in the North Pacific, 5 stations northeast of the Hawai- 

 ian Islands, 7 stations in the North Equatorial Current 

 north of the Marshall Islands, and 3 stations between 

 Guam and Tokyo; in the South Pacific, 2 stations east of 

 the Samoan Islands, and 5 stations between the Galapa- 

 gos and Easter Islands (fig. 61). There are 32 records 

 of occurrence: 30 rare and 2 occasional. The species 

 was found about equally at the 3 levels, with 10 records 

 for the surface, 12 for 50 meters, and 10 for 100 me- 

 ters. There are 24 net records and 8 pump records. 



This tropical species reached its greatest distance 

 from the equator in the western Pacific, where it oc- 

 curred almost to 35° north (station 113). In the eastern 

 Pacific it was found only to 33° north (station 145). In 

 the South Pacific it was not found south of 19° south. 

 The 2 records of "occasional" were in the North Equa- 

 torial Current (stations 100 and 101). 



The surface temperatures at the stations where the 

 species occurred at any depth varied from 22°.4 to 

 28°5 C. The ranges of hydrographic conditions in situ 

 were as follows: temperature, 16°0 to 28°6 C; salinity, 

 34.1 to 36.3 o/oo; pH, 8.16 to 8.39; phosphate, 3 to 40 

 mg P04/m^. 



It may be concluded from the Carnegie observations 

 that A. spinifera is a very rare but widely distributed 

 tropical species, seldom collected because of its sparse 

 numbers. Water of low nutrient content is no barrier 

 to it, as 18 of the 32 records were from water with less 

 than 10 mg P04/m^. 



Genus SPIRaULAX Kofoid 



Diagnosis . Plate formula: 4ap, la, 6pr, 6g, 6s, 

 6po, Ip, lant. First apical does not touch girdle or an- 

 terior extension of ventral area. Posterior intercalary 

 wide. Sulcal plates: as, ra, rs, Is, i, ps. Ventral epi- 

 thecai pore absent. 



Comparisons . Spiraulax is closely related to Gon - 

 yaulax . It has the same number of plates in all regions 

 of the theca, but the arrangement of the plates in the two 

 genera is significantly different. In Spiraulax there are 

 four apicals and only one anterior intercalary. In Gon - 

 yaulax pacifica and G. fusiformis there are only three 

 apicals, but there are two, instead of one, intercalaries. 

 The intercalary in Spiraulax is probably homologous 

 with a2 in Gonyaulax, whereas al of Gonyaulax is prob- 

 ably homologous with the third apical in Spiraulax . In 

 Gonyaulax the first apical extends either entirely to the 

 girdle or to the anterior end of the ventral area; in 

 Spiraulax this plate lies at the anterior edge of first pre- 

 cingular. The apical limb of ap2 and the ventral epithe- 

 cal pore foimd in Gonyaulax are absent in Spiraulax . 



The hypothecal plate patterns are the same in the 

 two genera, although pi is usually narrower in Gonyau - 

 lax . The ventral area of Spiraulax is similar to that of 

 G. fusiformis , but G. pacifica has one more sulcal plate. 



Spiraulax is less closely related to Acanthogonyau - 

 lax than to Gonyaulax . Acanthogonyaulax has nine, in- 

 stead of six, precingulars; it has no anterior intercala- 

 ries; the first apical does not extend to the girdle; and 

 the ventral area is unique (see pp. 5-6). 



Remarks . The Carnegie material is similar to 

 that described and figured by Kofoid (1911b) from the 

 San Diego region. Our diagnosis of the pattern of the 

 major body plates agrees with that of Kofoid. The pat- 

 tern of the ventral area has not been reported before. 



Kofoid (1911b) identified his material with that of 

 Murray and Whitting (1899) published under the name 

 Gonyaulax j olliffei . He considered this species to be 

 generically distinct from Gonyaulax and established the 

 new genus Spiraulax to include the one species. In our 

 opinion, Kofoid was justified in doing this for his own 

 material, which is specifically the same as ours. Gon- 

 yaulax j olliffei Murray and Whitting, however, is prob- 

 ably more closely related to G. fusiformis n.sp. than to 

 Spiraulax (see above). Since it is impossible to deter- 

 mine the plate pattern in this species without dissection, 

 the figures given by Murray and Whitting (1899, pi. 28, 

 fig. la, b) probably do not show the correct plate pat- 

 tern, as these authors apparently did not dissect their 

 specimens. The shape of the body of their species is 

 not that of Spiraulax . Although the first apical is shown 

 not reaching the ventral area or girdle, on the other 

 hand, the accompaniment of this condition in Spiraulax. 

 i.e., the intercalary touching the first precingular, is 

 not shown. In fact, no intercalary plates are shown at 

 all. The ventral epithecal pore and slender first apical 

 are not shown, but these are very easily overlooked in 

 undlssected specimens. In G. fusiformis the presence 

 of the slender first apical would never be suspected 

 without dissection. 



