FRUCTIFICATIONS FROM THE MAZON CREEK FLORA 19 



Comparison.— These spores as sporae dispersae are most similar to Punc- 

 tatisporites minutus (Kosanke) Peppers, 1964. Kosanke (1950, p. 15-16) described 

 this species from the Mattoon Formation (upper Pennsylvanian) of Illinois and gave 

 a size range of 27.3 to 32.5 |am. Peppers (1964 and 1970) included within the 

 taxon spores having the same morphology but as small as 15 \im. From more re- 

 cently obtained data (Peppers, work in progress) from coals of the Mattoon For- 

 mation, it is thought that two rather distinct size ranges are represented: one 

 spore has a size range of about 25 to 33 jxm as originally given by Kosanke, and 

 the other has a size range of about 15 to 25 \im. Although spores of both size 

 ranges usually occur together in the Mattoon Formation, the spores of the larger 

 size range become dominant at about the middle of the Mattoon Formation. 

 The holotype of Punctatisporites minutus came from these strata. The size 

 difference is apparently useful in age determination and correlation of strata 

 in the Illinois Basin. £. minutus (small and large) occurs throughout the 

 Pennsylvanian in the Illinois Basin. It is uncommon from the base of the Penn- 

 sylvanian through the Spoon Formation, common in the Carbondale, Modesto, and 

 Bond Formations, and very abundant in the Mattoon Formation. This species cor- 

 responds to the species cf. Fabasporites Sullivan, 1964, of Clendening (1967), 

 except that Fabasporites is described as being alete. Clendening stated that 

 Fabasporites is very abundant in the Monongahela and Dunkard strata of the Ap- 

 palachian Basin. It is of interest to note that this increase in abundance of these 

 spore taxa toward the top of the Pennsylvanian corresponds to an increase in dis- 

 tribution of the form-genus Pecopteris . 



Asterotheca (ex Pecopteris) cf . miltoni 

 pi. 11, figs. 1-3 



Description.— Specimen ISM 15382 most probably belongs to the species 

 Asterotheca (ex Pecopteris) cf . miltoni . The preservation is relatively poor and 

 the sporangia are filled mainly with mineral matter. 



The spores are radially symmetrical, trilete, and circular to subcircular 

 in equatorial view, and secondary folding is common. Laesurae are often obscured 

 and are about two- thirds the length of the spore radius. Labra are 1 to 2 |im wide. 

 The exine is covered with grana that are circular to subcircular in plan view. They 

 are about 1 [±m in diameter and usually wider than high. About one-half the spore 

 surface area is occupied by grana. Some grana touch at their bases or are joined, 

 and 65 to 80 grana extend beyond the spore margin. The exine is about 1 |am 

 thick. The diameters (35 specimens) range from 37 to 58 [im, with an average of 

 49 |im. 



Comparison.— If found isolated, this spore would be assigned to Cyclo- 

 qranisporites . It is similar to Cyclogranisporites cf. minutus Bharadwaj, 1957 

 as illustrated in Smith and Butterworth, 1967. These spores are very similar to 

 those described from Asterotheca (ex Pecopteris) miltoni by Potonie (1962) and 

 Laveine (1970). 



Discussion 

 The sporangia are preserved in more or less three-dimensional form and 

 filled with brown masses of spores and with white mineral matter. The cell wall 

 has been destroyed and a cell pattern is not visible. In this type of preservation 

 it is impossible to see any difference between Asterotheca , Acitheca, Scolecop- 



