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ILLINOIS STATE GEOLOGICAL SURVEY 



217 fx (mean 172.5 ll for 65 specimens); 

 breadth from 113 to 179 yu. (mean 145 ll for 

 59 specimens) ; length-breadth ratio (text 

 fig. 5) averaging 1.19. Monolete suture dis- 

 tinct, in some specimens open, averaging 57 

 percent (range 44 to 86 percent) of the 

 spore length, between extremes of 75 ll and 

 151 fi. Suture terminations usually masked, 

 in proximo-distal compressions (pi. 15, fig. 

 5a) , by an arcuate thickening of the spore 

 coat. Thickening most conspicuous around 

 the ends of the sutures (pi. 15, fig. 4) , some- 

 times extending as an elongate oval band 

 completely around suture. Lips difficult to 

 distinguish, membranous, up to 3.7 ll in 

 height. 



Spore coat bearing characteristic and 

 unique type of punctate ornamentation. 

 Discrete puncta or pores, completely trav- 

 ersing spore coat and appearing larger at 

 outer surface of coat, scattered randomly 

 over spore coat (pi. 15, fig. 5a), commonly 

 10 to 20 ll apart. Generally two fairly well 

 defined subcircular areas of closely spaced 

 punctae, also completely traversing spore 

 coat (pi. 15, fig. 5b) , occurring at the geo- 

 metrical equator on either side of the su- 

 ture, roughly in the median transverse 

 plane (pi. 15, fig. 5a) . Puncta group meas- 

 uring 25 to 40 ll across, sometimes much 

 larger. 



Spore coat highly translucent, golden yel- 

 low to yellowish brown by transmitted 

 light; coat from 2.5 to 10 ll thick, thickest 

 near terminations of suture (pi. 15, fig. 4) . 



Holotype. — Maceration 625B-f slide 2, 

 lower part of the Willis Coal, Gallatin 

 County, Illinois (pi. 15, figs. 5a, b) . 



Discussion. — The histogram presented in 

 text figure 5 characterizes the shape of these 

 spores. The few specimens that possess 

 longitudinal folds are not included. There- 

 fore, the slight skewness — more spores tend- 

 ing beyond the mean towards the elongate 

 rather than isodiametric proportions — can- 

 not be an expression of the tendency to 

 form elongate folds as it is for spores of 

 Monoletes ovatus (Schopf, 1938, fig. 2, p. 

 44) . In comparison to spores of M. ovatus, 



these spores tend to be more isodiametric in 

 shape. 



The actual measurements of length and 

 breadth are shown in text figure 4. Al- 

 though 126 ll is given in the text above as 

 the minimum spore length observed, this is 

 not indicated on the histogram (text fig. 4) 

 because the breadth of this spore is not 

 measurable. 



The spore coat has a high translucency, 

 somewhat similar to that of the larger 

 spores of Calamospora. It may appear 

 thicker (pi. 15, fig. 5b) in the area of the 

 puncta groups. The puncta and suture do 

 not show as clearly on unstained specimens 

 as on the stained ones (compare figures 4 

 and 5a on plate 15) . 



Although the groups of puncta are gen- 

 erally two in number, one on either side 

 of the suture, there is some variation in the 

 number, position, and size of the groups. 

 The holotype (pi. 15, figs. 5a, b) and the 

 spore shown by figure 4 on plate 15 are typi- 

 cal examples. On the latter spore one 

 puncta group is in sharp focus whereas the 

 other, on the opposite side of the spore, is 

 out of focus, just above and to the right in 

 the photograph. 



A few spores have scattered discrete 

 puncta; one has three groups of puncta; 

 another has two puncta groups covering at 

 least half the spore coat area; the largest 

 spore is completely covered with closely 

 spaced puncta. Worn or poorly preserved 

 spores merely have shredded holes in the 

 coat at the position of the puncta groups. 

 Those specimens that do not have puncta 

 groups appear shallowly infrapunctate. It 

 is possible that this ornamentation is initi- 

 ated on the inner surface of the spore coat. 



Occurrence. — Renisporites confossus is 

 abundantly represented in the lower part 

 (maceration 625B) , but less abundantly in 

 the upper part (maceration 625A) of the 

 Willis Coal, Gallatin County, and in the 

 Tarter Coal (maceration 901), Warren 

 County, Illinois. A poorly preserved spore, 

 questionably referable to this species, was 

 found in a coal in the Mansfield (?) Forma- 

 tion (maceration 779) in Indiana. 



