FAMILY GONYAULACACEAE 



53 



Acanthogonyaulax spinifera 



(Murray and Whitting) Graham 



(Figures 64, 65) 



Ceratocorys spinife ra Murray and Whitting, 1899, p. 



329, pi. 30, figTBa, b, e (not fig. 6c, d). 

 Gonyaulax ceratocoroides Kofoid, 1910, p. 182. Kofoid, 



1911a, pp. 202, 247. Pavillard, 1931. p. 50, pi. 2, 



fig- 2. 



Dimensions . Length (h), measured in ventral view 

 from apex to posterior end of sulcus, 63 (55-75) mi- 

 crons. Diameter (d) 49.5 (42-58) microns. Length of 

 ventral spines 23 (5-31) microns, or about 5 girdle 

 widths for the average.' Girdle width 4-5 microns. 

 Thirteen specimens were measured. 



Shape . Strongly resembles Ceratocorys in general 

 appearance because of angularity of body and prominent 

 brushlike spines on hypotheca (figs. 64B and 65). Body, 

 including apical horn, somewhat longer than broad. The 

 h/d ratio is 1.27 (1.19-1.44). Body nearly circular in 

 girdle region (fig. 64C, E) but hypotheca very angular 

 posteriorly (fig. 64B, C). Epitheca rather low but ex- 

 tended as a tubular horn along its distal quarter. Be- 

 sides the constriction formed by the base of this horn, 

 there is another constriction halfway to girdle, promi- 

 nent only on the right side. Thus, there are two shoul- 

 ders on epitheca which are most distinct on the right 

 side of body (fig. 64B). Hypotheca squarish in outline, 

 sometimes with a constriction in the middle, at least ol 

 one side, usually the right (fig. 64B); truncated posteri- 

 orly. Antapex squarish and sunken in center (fig. 64B, 

 C). A bulge occurs on hypotheca at base of each ven- 

 tral spine. Girdle sinistral, displaced about 3 girdle 

 widths, not excavated; no overhang. 



Ventral area narrow anteriorly but flares out pos- 

 teriorly to full width of antapex into a bilobed area. 

 Sulcus a deep, narrow groove occupying entire anterior 

 half of ventral area and obscured by various lists asso- 

 ciated with it (figs. 64B, 65). Flagellar pore occurs op- 

 posite distal end of girdle; almost hidden by overhang 

 of postcingular and right sulcal plates. 



Plate pattern . The three apical plates are of une- 

 qual size. The first is narrow and ventral, and extends 

 only about two-thirds of way to girdle. It bears the ven- 

 tral eplthecal pore. The second and third apicals, only 

 half as long as the first, are broad and compose most 

 of apical horn (fig. 64B, E). Apical closing platelet 

 present. Anterior intercalary plates absent. Of the 

 nine precingular plates, the first three are minute 

 plates, just anterior to ventral area. The other six are 

 subequal in size and comprise the larger part of epithe- 

 ca (fig. 64E). The six girdle plates subequal in size. 

 (Girdle sutures Indicated by arrows in fig. 64E.) First 

 postcingular is a small narrow plate overhanging sulcus 

 as in Gonyaulax (fig. 64A, B). The other five postcingu- 

 lars large and subequal in size (fig. 64C). The posteri- 

 or intercalary plate lies between left side of ventral 

 area, the second and third postcingiilars, and the antap- 

 Ical plate. The antapical plate Is large and squarish, 

 constituting the truncated antapex. Its four long sides 

 border the third to fifth postcingulars and the posterior 

 sulcal plate, but it also has two relatively short sides 

 bordering the posterior intercalary and the sixth post- 

 cingular plates (fig. 64C). 



Ventral area composed of seven plates. The poste- 

 rior sulcal plate Is the only large one and forms a ma- 

 jor part of the ventral aspect of hypotheca (fig. 64A, D). 



Other sulcal plates minute. The anterior sulcal plate is 

 opposite the proximal end of girdle. It has no anterior 

 projection into epitheca. Posterior to this plate and just 

 anterior to flagellar pore are the right accessory and 

 left accessory sulcal plates. Between flagellar pore anc 

 posterior sulcal plate are three plates: on the left side 

 of left sulcal plate; on the right side, the right sulcal 

 plate; adjacent to the pore and between the last plate and 

 the posterior sulcal plate there Is an intercalary sulcal 

 plate (fig. 64A, D). Right sulcal plate overhangs pore in 

 such a way that it is ventral to left sulcal plate (fig. 65). 



Thecal wall . Surface of larger body plates covered 

 with deep pits regularly spaced. Pores not demonstrat- 

 ed in these pits. Second and third precingular plates, 

 but not the first, with pores. Girdle plates with two 

 rows of pores. Ventral eplthecal pore occurs on right 

 edge of first apical plate. 



Lists and spines . Lists and spines reach a high de- 

 velopment in this species. Girdle lists are usually a- 

 bout 3 girdle widths wide, strengthened by heavy ribs 

 which are connected to numerous heavy listlike cross 

 ribs on girdle plates (figs. 64C, E, 65). Strong lists bor- 

 der all margins of ventral area. Right sulcal list at- 

 tached to sixth postcingular plate. Left sulcal list at- 

 tached to first postcingular and posterior Intercalary. 

 These two lists extend onto ventral antapical spines. 

 Anterior (eplthecal) right sulcal list attached to ninth 

 precingular plate. It borders right margin of eplthecal 

 part of ventral area between girdle ends and extends 

 somewhat beyond, anteriorly. Body lists well developed 

 along all sutures of hypotheca and along all sutures of 

 larger precingular plates. Apical plates, however, sin- 

 gularly free of lists (figs. 64B, E, 65). All body lists 

 extending to girdle run out to edge of girdle lists. The 

 body lists often strengthened by irregularly scattered 

 ribs, usually extending out from base of Ust. 



Long spines with "brushes" are a prominent fea- 

 ture of this species. These spines are formed at cer- 

 tain junctions of body lists. The two most prominent 

 spines are at the ventral corners of antapical plate; two 

 other antapical spines occur at the dorsal corners of 

 this plate. The fifth spine is left lateral in position, be- 

 ing located at left corner of the posterior Intercalary. 

 The "brushes" consist of secondary thickenings running 

 out from the primary thickening which composes the 

 body of this spine at the list junction. 



Variation . Size and shape of body fairly constant. 

 The greatest variation occurs in the lists and spines. 

 The variations may represent growth stages. Length of 

 ventral spines, however, constant: from 20 to 31 mi- 

 crons except for one specimen with spines 5 microns 

 long. Displacement of girdle varies more than in most 

 species of Peridiniales; a continuous series with dis- 

 placements from 1.5 to 4 girdle widths was found. 



All our specimens had five spines, although In one 

 case one spine was double. Murray and Whitting (1899) 

 stated that the usual number of spines Is six and that 

 they found one specimen with only two. Whether the 

 former value should be accepted may be considered 

 doubtful. Since the spines are developed at the junction 

 of lists, however, a maximum number of seven seems 

 possible. The spines may be straight or curved. Cur- 

 vatures are particularly evident in Murray and Whit- 

 ting's figures. Outer margins of lists may be straight 

 or very much indented in parts between spines or be- 

 tween spines and girdle list. 



Historical . Murray and WhItUng (1899) described 



