FAMILY CERATOCORYACEAE 



35 



otner species more anteriorly, reaching the most ante- 

 rior position in C. gourretii and C. horrida . The e/1 

 ratio varies from 0.16 in C. gourretti to 0.46 in C. re - 

 ticulata . Girdle displaced from 0.5 to 2.5 girdle widths; 

 its ends separated by anterior end of ventral area. 



Angularity of body pronounced in lateral view, ex- 

 cept in C. gourretii , which is circular to ovate, mother 

 species epitheca triangular or triangular with truncated 

 apex. Hypotheca, in lateral view, squarish to triangular, 

 but always with an oblique shearing posteroventrally 

 (except in C. gourretii ) which displaces the posterior 

 end of the sulcus some distance from antapex, some- 

 times as much as half the distance to the girdle. In C. 

 bipes the shape characteristic of the genus somewhat 

 obscured by presence of two posterior lobes, one ven- 

 tral and one dorsal. 



Greatest width of body is at girdle in all species ex- 

 except C. gourretii and C. horrida . In the former spe- 

 cies, this occurs about midway between girdle and ant- 

 apex, and in the latter species, just posterior to girdle. 



In ventral view, also, body is quite angular in most 

 species. Epitheca dome-shaped to triangular in all spe- 

 cies, but may be very low in C. g ourretii and C . horrida . 

 Hypotheca triangular to squarish. Degree of "squarish- 

 ness" expressed by the angle /9. This angle was not 

 measured in C. horrida and C. g ourretii . as their later- 

 al edges are not straight, making accurate measure- 

 ments impossible. Fortunately, determination of this 

 angle is not necessary for the differentiation of these 

 species. Ceratocorys horrida is the most squarish of 

 the genus, and its antapex is the broadest; C. g ourretii 

 is rounded antapically. In other members the most tri- 

 angular is C. reticulata , with an average angle /3 of 37°. 

 The other species vary between this value and 15°.5, 

 which is found in C. skogsbergii . 



Plate pattern. For plate formula, see family diag- 

 nosis (p. 32). Number of plates, twenty-nine, constant. 

 Apical pore covered by a closing apical platelet, as in 

 Gonyaulax ; a platelet not attached to any body plate. 



There are four plates in apical region, but only two 

 of these may be considered apical plates, as the other 

 two do not touch the apical closing platelet (fig. 47C). 

 First apical squarish and surrounds left and dorsal edg- 

 es of platelet; second apical is an elongated ventral plate 

 and surrounds right and ventral edges of apex. First 

 anterior intercalary squarish and lies to the right of a- 

 pex between apicals 1 and 2. Second anterior intercala- 

 ry, like second apical, very narrow and lies along left 

 edge of second apical although it does not touch apex; 

 bears ventral epithecal pore. 



The first three precingular plates occupy the first 

 three quadrants of the epitheca, and the fourth and fifth 

 occupy the fourth quadrant (fig. 44B). Fifth precingular 

 is smaller than the rest and lies posterior to second an- 

 terior intercalary and second apical plates. 



There are six girdle plates of approximately equal 

 length. 



There are five or six postcingulars; when five, 

 there is an extra plate in the sulcus, the homologue of 

 the first postcingular. For this reason the numbering of 

 the plates is kept uniform in all species, so that in the 

 species with only five apparent postcingulars (C. gour - 

 retii and C. skogsbergii ) the extra sulcal plate is des- 

 ignated postcingular 1. Postcingulars 1 and 2 are small 

 and always separated from 3 by a prominent list. Post- 

 cing\ilars 3 to 6 are large and comprise, along with the 

 antapical plate, the main Iwdy of the hypotheca. Poste- 



rior intercalary lies to the left of sulcus between post- 

 cingulars 1 and 2, and antapical plate. 



The single antapical plate occupies most of the ant- 

 apex but is displaced to the right so that the left edge of 

 antapex is formed by the turned-under edges of the third 

 and fourth postcingulars, which are much longer than 

 the postcingulars of the opposite side (fig. 47 A, B). 



Ventral area composed of five or six plates (figs. 

 44 A, 58A): an anterior, a posterior, a left, a right, a 

 right accessory, and sometimes a left accessory which 

 is homologous with the first postcingular in other spe- 

 cies. When the flagellar pore is long, it may border the 

 right sulcal plate for half its length (C. horrida , fig. 47B), 

 but usually the left plate extends so far anteriorly that 

 the pore is quite remote from the right plate (C. aultii. 

 fig. 56A). 



The plate pattern in Ceratocorys is remarkably con- 

 stant. In the main body plates practically no variations 

 were found. This is in striking contrast to the condition 

 in the genus Peridinium . where there are interspecific 

 differences as well as variations within the species. In 

 the ventral area of Ceratocorys there are variations to 

 be described below, but the number of plates is constant. 



Body wall . Surface smooth to rugose and pitted in 

 all species except C. reticulata , which has a heavy retic- 

 ulation. Girdle with two rows of pores. Pores also oc- 

 cur in sulcal plates and in main body plates. In C. retic - 

 ulata pores not demonstrated, but probably present. 



Flagellar pore approximately on a level with distal 

 end of girdle. Apical "pore" covered by a platelet as in 

 Gonyaulax . Ventral epithecal pore about midway be- 

 tween apex and girdle on riglit edge of second anterior 

 intercalary plate near its posterior end. This also re- 

 calls Gonyaulax . 



Lists. Girdle lists attain their greatest width in C. 

 horrida . Usually with short, strengthening ribs running 

 radially. In addition to these ribs other heavy rlbllke 

 structures may be seen when the specimen is viewed in 

 apical or antapical aspect. These are not girdle list 

 ribs, but transverse girdle lists seen on end (figs. 49E, 

 54C). They are attached to the girdle, are spaced at 

 fairly regular intervals, and may attain a width exceed- 

 ing 1 girdle width and divide the girdle into a series of 

 chambers. 



Lists may be developed at the borders of all plates 

 and, in addition, on the surface of the antapical plate. 

 Lists of C. horrida particularly wide and prominent. 

 Two lists are especially important: a list extending veh 

 trally from right edge of po3, the ventral body list ; and 

 one extending dorsally from dorsal edge of po4, the dor - 

 sal bod y list. In C. horrida and C. gourretii these bear 

 prominent spines. 



In addition to these two lists and to the posterior 

 clngular list, there are, on the hypotheca, four nonspin- 

 ulate lists. The right sulcal list runs along left edge of 

 po6 and is continuous with distal end of posterior girdle 

 list. The left sulcal list is attached along right edge of 

 pol or po2 and of posterior intercalary plate, joining 

 posterior cingular list anteriorly and, sometimes, con- 

 tinuous with list of ventral antapical spine posteriorly. 

 The right lateral and left lateral lists run from posteri- 

 or cingular list down lateral sides of body a short dis- 

 tance; the former list at ventral edge of po5, the latter 

 at ventral edge of po4. These two lists may be absent. 



Lists of the epitheca more variable than those of 

 other parts of body. In general there is a list for each 

 suture, although in old specimens the list may not be im- 



