DENSO-SPORITES 



39 



possible to establish accurately from sec- 

 tions the proximal position of the suture 

 and the distal location of the harmome- 

 gathic grooves. The fact that spores are 

 frequently found with the suture opened 

 but, except in instances of obvious me- 

 chanical or chemical injury, have never 

 been observed with the umbo split off as 

 an "operculum" or the grooves other than 

 intact, strongly suggests that proximal 

 gametophytic exit was still a fundamental 

 feature of these forms as it must have 

 been in their more ancient cryptogamic an- 

 cestry. Such spores are also regarded as 

 prepollen (cf. Schopf, 1938, pp. 14-15). 



The foregoing diagnosis serves to cor- 

 rect some erroneous interpretations of 

 structure previously held; e.g. the "en- 

 circling ridge" described by Schopf (1938, 

 p. 45) for the species designated as Mono- 

 letes ovatiis, is the margin of the distal 

 grooves discussed here. It has no hapto- 

 typic significance although it possibly is 

 not emphytic in origin in the same sense 

 that ordinary surface ornamentation is. 



Monoletes was first used by Ibrahim in 

 1933 to designate a new group in his ar- 

 tificial system. Although substantive in 

 form and similar to a generic name, it 

 was not originally applied in that sense 

 and no nomenclatural type has been pre- 

 viously proposed. It has been used as a 

 ,eeneric designation and applied more nar- 

 rowly (Schopf, 1936, 1938) ; we now 

 emend it to correspond with the restricted 

 usage. Monoletes ovatus Schopf may 

 serve as the type species of the genus. 

 The group now includes two species, 

 both of which appear to be widely dis- 

 tributed. It is likely that further species 

 will be distinguished by application of 

 more refined biometric procedure. Both 

 species must still be regarded as rather 

 generalized types. 



1. Monoletes ellipsoides (Ibrahim) Schopf, 

 1938, Illinois Geol. Survey Rept. Inv. 50, 

 p. 45, pi. 1, fig. 14; pi. 6, figs. 5 and 6. 



Sporonites ellipsoides Ibrahim, 1932, 

 Neues Jahrb. Beilage-Band 67, Abt. B., p. 

 449, pi. 17, fig. 29. 



Laevigato-sporites ellipsoides (Ibra- 

 him) Ibrahim, 1933, Sporenformen des 

 Aegirhorizonts, p. 40, pi. 4, fig. '29. 



Punctato-sporites ellipsoides (Ibrahim) 

 Loose, 1934, Inst. Palaobot. Arb., vol. 4, 

 no. 3, pp. 158-9, pi. 7, fig. 35. 



Sporites ellipsoides (Ibrahim) Wicher, 

 1934, idem, vol. 4, no. 4, p. 185. 



2. Monoletes ovatus Schopf, 1935, Illinois 

 Acad. Sci. Trans, vol. 28, no. 2, p. 108, fig. 7. 



Pollen of Dolerophyllum sp., Zerndt, 

 1930, Acad, polonaise sci. Bull, internal., 

 ser. B, pp. 55-56, pi. 8, figs. 42-49. 



Type 31 Zerndt, 1931, idem, ser. A, p. 

 176. 



Monoletes ovatus Schopf, 1935, Illinois 

 Acad. Sci. Trans, vol. 28, no. 2, p. 176. 



Monoletes ovatus Schopf, 1938, Illinois 

 Geol. Survey Rept. Inv. No. 50, pp. 43-45, 

 pi. 1, figs. 3-5, pi. 6, figs. 1-4. 



Pollen of Dolerotheca fertilis, Zerndt, 

 1940, Paleontographica, vol. 84, Abt. B, p. 

 136-138, pi. 11, fig. 36. 



Genus Denso-sporites (Berry, 1937), 

 emend., S. W. and B. 

 Plate 1, figures 9-9c 



Symmetry. — Spores radial, trilete. 



Shape. — Originally oblate, round to 

 subtriangular in equatorial outline. When 

 compressed, the central area becomes 

 much thinner than the margins due to va- 

 riation in spore wall thickness. Coal thin 

 sections, taken vertically through the coal 

 bed, show them compressed into a "dumb- 

 bell" shape. The original highly oval sec- 

 tional form results in extremely uniform 

 proximo-distal orientation in enclosing 

 sediments. 



Sise. — Diameter of specimens assigned 

 among various species varies from about 

 35 to 100 microns. 



Ornamentation. — Smooth to apiculate 

 and rugose. External surface character, 

 typically is uniform, though ornamenta- 

 tion may be more strongly developed to- 

 ward the equator in some forms. 



Haptotypic structures. — A delicate tri- 

 lete marking is visible in well preserved 

 material or where the central area of the 

 proximal surface is consistently present. 

 "Fissures" penetrating to the margin in 

 some instances may be essentially hapto- 

 typic continuations of the trilete sutures. 



Spore coat. — Characterized by great 

 differences in thickness. The proximal 

 and distal walls are usually membranous, 

 or at least significantly thinner than the 

 equatorial portion of the coat. The latter 

 area is oftentimes so thick it is practically 

 opaque to transmitted light in contrast to 

 the highly translucent central area. It 

 may also be so extended centrifugally as 

 to simulate a flange but it is not usually 

 strictly demarcated from the spore body, 

 as such. 



