GENUS DENSO-SPORITES 



31 



GENUS Denso-sporites (Berry, 1937) 

 emend., S. W. and B, 1944 



Plate 6, figures 1-11; Plate 7, figures 1-2 



The genus Denso-sporites has an interest- 

 ing and important geological range in Illi- 

 nois. So far as is known, it is restricted 

 entirely to Tradewater and Caseyville 

 groups. Maximum abundance is attained 

 in the Reynoldsburg coal bed, upper Casey- 

 ville, and the youngest Denso-sporites 

 horizon is the Dekoven coal bed, upper 

 Tradewater. 



Thiessen's "splint microspores" were 

 species of Denso-sporites, and he found this 

 type of spore abundantly preserved in splint 

 coals. The resulting idea that splint coal 

 was derived from a specific type of vegeta- 

 tion does not appear valid. If this were 

 true one might expect to find splint spores 

 wherever splint coal is encountered. Also, 

 the range of splint coal w 7 ould be identical 

 with the range of "splint microspores." 

 In Illinois, this is not true; in fact the 

 Reynoldsburg coal bed is not truly a splint 

 coal and yet it contains more "splint micro- 

 spores" than any other Illinois coal bed. 

 Figures 1-2, Plate 15, illustrate this point. 

 There is little information concerning splint 

 coal in Illinois; however it is known that 

 splint coal does occur above the range of the 

 "splint microspores." The parent plants 

 of Denso-sporites contributed to splint coal 

 but it is probable that splint coal was 

 formed in more than one way and from 

 more than one type of vegetation. 



The following are new species of Denso- 

 sporites: 



1. D. sinuosus 



2. D. glandulosus 



3. D. granulosus 



4. D. lobatus 



5. D. reynoldsburgensis 



6. D. ruhus 



7. D. sphaerotriangularis 



8. D. triangularis 



The following description of the genus 

 Denso-sporites is based on six previously 

 described species and the species mentioned 

 above: Spores are radial, trilete; isolated 

 compressed forms are round, oval to sub- 

 triangular in transverse plane. In vertical 



thin-section they are "dumbbell" shaped as 

 seen on plate 15, figure 1. The known 

 size range is from 27 to 100 microns. The 

 proximal-distal portions of the spore coat 

 may be levigate, granulose, punctate, papil- 

 late, apiculate, rugose, to vermiculate. The 

 equatorial portion of the spore coat may be 

 levigate, granulose, punctate, nearly retic- 

 ulate, rugose, apiculate and frequently 

 irregularly thickened. The trilete mark 

 may be indistinct, distinct, or even absent 

 if the proximal area of the spore coat is 

 poorly preserved. The rays may be limited 

 to the proximal area or extend into the 

 thicker equatorial portion of the spore coat. 

 The spore coat is always characterized by 

 the proximal-distal portion which is thin 

 and the equatorial portion which is much 

 thicker and frequently opaque. The parent 

 plants of Denso-sporites are unknown. In 

 some cases, the equatorial portion of the 

 spore coat resembles a flange which re- 

 motely resembles the spore genus Cirratri- 

 radites. 



Denso-sporites sinuosus sp. nov. 



Plate 6, figures 1-2 



Description. — Spores are radial, trilete, 

 roundly triangular to oval in outline and 

 frequently obliquely compressed. The 

 holotype (figure 1) measures 39.9 X 46.2 

 microns and the known size range is from 

 36 to 48 microns. The proximal and distal 

 portions of the spore coat are minutely 

 punctate. The thicker equatorial portion 

 is nearly opaque with ridges arranged so as 

 to appear reticulate to wavy. Figures 1-2, 

 plate 6, illustrate this feature. The trilete 

 mark is usually visible although indistinct 

 in some forms. The rays are not known to 

 extend beyond the proximal portion of the 

 spore coat. The proximal and distal por- 

 tions of the spore coat are thin but the 

 equatorial portion averages about 10.5 mi- 

 crons in thickness. Over 50 percent of the 

 spore coat is of the equatorial type as viewed 

 transversely. 



Holotype. — Maceration 587 Slide 12, 

 Battery Rock coal bed, Hardin County, 

 Illinois. 



Discussion. — The ornamentation of the 



