8 ILLINOIS STATE GEOLOGICAL SURVEY CIRCULAR 463 



are usually indistinct because of secondary folds. Labra are up to 1 \±m wide. 

 Ornamentation consists of closely spaced projections, intermediate between conate 

 and papillate, with gradually tapered round ends. Projections are about 1 urn wide 

 basally and 1.0 to 1.5 \im long; several projections sometimes are joined to form 

 small ridges, and ridges, in turn, are interconnected on some spores to form a 

 punctate or loosely reticulate pattern (pi. 2, figs. 5, 6). The spore wall is less 

 than 1 |am thick. 



A considerable difference in spore diameters was observed in preparations 

 from the two halves of one specimen (USNM 13385 and USNM 13386). Thirty-two 

 spore diameters (slide USNM 13385) indicate a range of 19 to 30 |j.m, with an av- 

 erage of 25 fim; thirty- five spore diameters (slide USNM 13386) show a range of 

 29 to 37 ^m, with an average of 33 \±m. The range for all the samples is 19 to 37 

 \±m, with an average diameter of 29 \xm. 



Stellatheca ornata (Lesquereux, 1884) comb. nov. Pfefferkorn 

 pi. 3, fig. 5; pi. 4 



1884 Pecopteris ornata Lesquereux, p. 760, pi. ill, figs. 30, 30b 

 (exclusive of figure 30a, which belongs to S.. latiloba) . 



1958 Pecopteris halli Lesquereux, in_ Langford, p. 172-173, fig. 299 

 (ISM 15830). 



1963 Pecopteris solida Lesquereux, in Langford, p. 215, fig. 827 

 (ISM 15830). 



Three specimens were examined, each with part and counterpart: 

 USNM 13387, USNM 13388 (Lacoe Coll. 1008b) from Mazon Creek, Illinois. 



Figured by Lesquereux (1884), holotype; 

 ISM 15548a, b (Langford Coll. 246 p-1) from near Wilmington, Will County, 



Illinois; 

 ISM 15830 from near Wilmington, Will County, Illinois. 



Description.— Pinnules (n-1) are semicircular or tongue-shaped, some- 

 times only lobe-like as in ISM 15548 (pi. 4, fig. 4). The pinnules, up to 3 mm 

 long and 2 mm wide, usually have indistinct midveins (n-1) and lateral veins (n) . 

 Pinnules (n-1) are attached along the entire base at an angle of about 50° and 

 are basally fused (text fig. 4). 



Pinnae (n-2) are 16 mm long and 5 mm wide on USNM 13387-8 and 18 mm 

 long and 6 mm wide on ISM 15548. Pinnae (n-2) are inserted at less than 60°. 



Pinnae (n-3), which are more than 7 mm long and about 30 mm wide, bear 

 pinnae (n-2) 7 to 10 mm apart. The pinna axis (n-3) is 1.4 to 2.0 mm wide and 

 only slightly winged. 



Superficial sori consist of 6 to 12 free sporangia, with most of the sporangia 

 forming a circle or an ellipse around one or two central sporangia. Sori are at- 

 tached at the end of lateral veins near the laminar margin and are 0.8 to 1.2 mm 

 in diameter. There are usually three (2 to 5) sori on a pinnule (n-1); no sori occur 

 on the laminar wing of the pinna axis (n-3). Sporangia are 0.2 to 0.3 mm in di- 

 ameter, and the wall pattern consists of elongate cells in longitudinal rows paral- 

 lel to the long axes of sporangia. No spores were present in the investigated 

 specimens. 



Discussion 



In describing the compression specimens of Stellatheca latiloba from the 

 northern French coal basin, Danze (1956) mentioned its similarity to Oligocarpia 



