46 



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



drawings, e.g., G. ostenfeldli Paulsen (1904), or with no 

 drawings at all, e.g., G. crassa and G. reticulata Kofoid 

 and Michener (1911). None of these can be included in 

 this genus with full certainty until more adequate de- 

 scriptions or figures are available. 



Comparisons . The genus Goniodoma is a distinct 

 unit with no close relatives (see p. 8). All regions of 

 the theca except the girdle are distinctive. The tabula- 

 tion of the epitheca is unique. Although other genera 

 have been reported with ten epithecal plates, none has 

 the combination of three apicals, no intercalaries, and 

 seven precingulars. The hypothecal pattern is almost 

 equally distinctive. It occurs elsewhere only in the ge- 

 nus Pachydinium Pavillard. 



The ventral area substantiates the distinctness in- 

 dicated by the larger body plates. The sulcal plates are 

 only five and are comparatively simple and flat. The 

 ventral area is rather flat and there is no well-defined 

 sulcus. The flagellar pore faces ventrally, so that it is 

 completely unobscured in ventral view. The ventral 

 area, thus, must be considered primitive as compared 

 with the highly complex areas of Peridinium and Gon- 

 y aulax with their development of intricate plates, deep 

 sulcus, and elaborate lists. 



As indicated on page 8, Goniodoma may be consid- 

 ered a primitive genus whose closest relative is Cerato - 

 cojys, although the two genera are quite widely separat- 

 ed. 



Goniodoma polyedricum (Pouchet) Jorgensen 

 (Figure 60) 



Goniodoma polyedricum Jorgensen, 1899, p. 33. Paulsen, 

 1907, p. 8. Paulsen, 1908, p. 33, fig. 42. Paulsen, 

 1931, p. 37. Lindemann, 1925, pp. 97-98, figs. 2-4. 

 Lebour, 1925, p. 90, fig. 26. Pavillard, 1931, p. 

 96. Matzenauer, 1933, p. 452. 



Goniodoma poiyhedricum , iiorti, iy22, p. 85, pi. e, fig. 



75. 

 Peridinium p olyedricum Pouchet, 1883, p. 42, pis. 20, 



Goniodoma acuminatum Stein. 1883, pi. 7, figs. 1-16, pi. 



8, figs. 1, 2. ButscWi, 1885, pL52, fig. 5a-c. Schfltt 



1887, figs. 13-16. Schutt, 1895, pi. 7, fig. 31, 1-3, 



pi. 8, fig. 30, 1-10. Schutt, 1896, p. 21, fig. 30. 



Aurivillius, 1898, p. 98. Cleve, 1900b, p. 245. 



Entz, 1905, figs. 65, 66. Wang and Nie, 1932, p. 



295, figs. 7, 8. 

 Ggnyaulax p olyedra Okamura, 1907, pi. 5, fig. 35a-c. 

 ? Peridinium acuminatum Ehrenberg, 1838, p. 254, pi. 



22, fig. f^ " 



Dimensions . Length of body (j.) 58 (40-93) microns. 

 Diameter (d) 65 (45-100) microns. Width of girdle 4 to 

 6 microns. Eighty-two specimens were measured. 



Shape . Body usually somewhat wider than long. The 

 1/d ratio is 0.90 (0.77-1.19). Body almost circular at 

 girdle but otherwise very angular (fig. 60A, B, H). An- 

 gles occur at almost all major body plate sutures. Epi- 

 theca angular dome-shaped without apical horn although 

 apex is well defined. Hypotheca broadly truncate poste- 

 riorly; antapex between one-third and one-half as broad 

 as diameter of body at girdle. Girdle nearly equatorial 

 sinistral; displaced from 1 to 2 girdle widths; slightly 

 concave; no overhang. Girdle continues onto ventral 

 area, where its ends are turned sharply posteriorly. 

 Ventral area short, broad, and angular, with a short pro- 

 jection of the anterior sulcal plate into the epitheca. 

 Flagellar pore ovate, on right side of ventral area at 



proximal end of girdle. It is evident in ventral view 

 without dissection. Sulcus only slightly developed. 



Plate pattern . Formula: 3ap, 7pr, 6g, 5s, 5po, 

 3ant. The three apical plates are about equal in size 

 and surround the apical platelet, which covers apical 

 pore (fig. 60A). This platelet is oval in shape and is 

 placed at an angle of about 45° to the dorsoventral axis 

 of the body. Precingular plates of approximately equal 

 size except the ventrally placed first and seventh, which 

 are about half the size of the others. The six girdle 

 plates subequal in size with sutures symmetrically 

 placed (fig. 60A). Postcingular plates also approximate- 

 ly equal in size, as are the antapicals (fig. 60B). Sec- 

 ond antapical composes most of the truncate antapex. 

 The first and third antapicals are more ventrally placed, 

 and each bounds half of posterior margin of ventral area. 



The ventral area composed of five plates: three 

 large posterior plates lying posterior to the girdle, and 

 two anterior ones representing extensions of girdle. 

 Anterior sulcal plate (as, fig. 60F, G, H) forms anterior 

 end and half right edge of flagellar pore and represents 

 the proximal extension of girdle into ventral area. It 

 has a limb extending into epitheca, posterior to prl. 

 The anterior cingular list is continued across it. The 

 left, posterior, and right sulcal plates are more or less 

 rectangular, of about equal size, and form greater part 

 of area. Left sulcal plate forms left edge of pore, the 

 posterior plate the posterior edge, and the right sulcal 

 plate is not in contact with the pore. Right accessory 

 sulcal plate forms an extension of the distal end of gir- 

 dle into ventral area. It has a narrow anterior limb 

 which extends to anterior sulcal plate to form the right 

 edge of pore. Thus, all sulcal plates border the pore 

 except the right. 



Surface. Entire body wall, including that of girdle 

 and sulcal plates, covered with large pits regularly ar- 

 ranged. These have pores in their centers which, in 

 optical cross section, can be seen to extend through body 

 wall. Thickness of body wall extremely variable and 

 depth of pits varies accordingly. Girdle bears two to 

 four rows of pits with pores, although only two rows are 

 ordinarily visible in ventral or lateral view as outer 

 rows are on curved sides of girdle. There is a ventral 

 epithecal pore situated on the anterior margin of prl 

 (fig. 60D, H). This pore is peculiar in not being covered 

 by a platelet or surrounded by a ridge or list. Body 

 plates joined by rabbet membranes which are rather 

 narrow compared with those in Peridinium . 



Lists. Cingiilar lists from 1.5 to 2.5 girdle widths 

 wide, always somewhat ornamented with spines and re- 

 ticulations, which are quite thick (fig. 60C). Posterior 

 list usually more heavily sculptured than the anterior 

 (fig. 60A, B). Each suture of main body plates marked 

 by a thick triangular list ridge. When these are viewed 

 along edge of body, they appear as thin lists because of 

 their transparency (fig. 60H, I). Along their outer mar- 

 gins they may be clear or bear reticulations. Proximal- 

 ly, however, they almost invariably bear large reticula- 

 tions or pits (fig. 60A, B, H). Lists surrounding ventral 

 area do not attain a greater development than that of the 

 body lists. No lists occur at sutures between sulcal 

 plates except between the left and posterior sulcal plates. 



Variation . The size varies considerably. In our 

 material both the length and the width showed a differ- 

 ence of over 100 per cent between the smallest and 

 largest specimens. Shape of body more constant. Most 

 of the material had anj/d ratio less than 1.00; in only 



