6 ILLINOIS STATE GEOLOGICAL SURVEY CIRCULAR 463 



Stratigraphic range: Lower Westphalian C to Westphalian D 

 Geographic distribution: Northern France and Illinois (U.S.A.) 

 The two species of Stellatheca that have been described, S. latiloba 

 (Danze, 1956) and S... ornata (Lesquereux, 1884) comb. nov. Pfefferkorn, p. 8, 

 are grossly separable by the smaller wings on the pinna axis (n-3) in S_. ornata , 

 which is known only from Illinois. 



Stellatheca latiloba Danze, 1956 

 pi. 1, figs. 1-5; pi. 2, figs. 1-10; pi. 3, figs. 1-4 



1880 Pecopteris lyratifolia Goeppert, in Lesquereux 1879 (Atlas), 1880 



(text), p. 259, pi. 48, figs. 4-4c. 

 1884 Pecopteris ornata Lesquereux, p. 760, pi. Ill, fig. 30a (exclusive 



of figs. 30 and 30b, which belong to Stellatheca ornata ) . 

 1956 Stellatheca latiloba Danze, p. 284-287, pi. 43, figs. 2-2b, pi. 



44, figs. 1, 2. 



Four specimens of Stellatheca latiloba were examined, two with both halves 



present and two with only one half of the ironstone nodule available. All are from 



Mazon Creek, Illinois. 



USNM 13385 (figured by Lesquereux, 1884) and USNM 13386 (Lacoe Coll. 1008a). 



USNM 13382 (Lacoe Coll. 643a) (figured by Lesquereux, 1880). 



USNM 13383 and 13384 (Lacoe Coll. 910a). Determined by Lesquereux as Pecop- 

 teris stellata Lesquereux, 1880, but does not agree with his figure and de- 

 scription. 



Description.— Pinnules (n-1) are semicircular in outline and continuous 

 basally with the wings of the pinna axis (n-2). Pinnules are 2 to 3.5 mm wide and 

 1 to 4.5 mm long, excluding the laminar wing of the pinna axis (n-2), which is 

 1 to 2.5 mm wide. The angle of pinnule (n-1) attachment to the pinna axis (n-2) 

 is less than 75°; the pinnules are attached along their entire bases and touch 

 each other laterally at the base. Sori are apparently marginal or very near the 

 margin, and the laminar margin sometimes extends over sori. Midveins (n-1) and 

 lateral veins (n) are usually indistinct. 



Pinnae (n-2) are tongue-shaped, distally tapered, and fused basally with 

 the laminar wings of the pinna axis (n-3). Pinnae (n-2) are 18 to 25 mm long, in- 

 cluding a laminar wing, and 5 to 13 mm wide. Pinnae (n-2) touch laterally at the 

 basal attachment but do not overlap, and the angle of attachment is 45°-90°. 



Pinnae (n-3) are more than 70 mm long and are 40 mm wide, and there are 

 nine pinnae (n-2) or more on each side. The winged lamina of the pinna axis 

 (n-2) is 4.0 mm wide. Two distinct ridges, apparently indicating the vascular 

 strand on the upper part of the pinna axis (n-3), are 0.4 mm apart. 



Sori are crowded together in groups on or near the laminar margin. Smal- 

 ler sori occur near the pinnule tip. A sorus consists of 6 to 15 free sporangia, 

 with most of the sporangia forming a circle or an ellipse around 1 to 3 central spo- 

 rangia. The long axis of elliptical sori is parallel with the laminar margin (text 

 fig. 3); there are usually 4 (3 to 6) sori on a pinnule (n-1) and none on the winged 

 part of any pinna axis (n-2, n-3). Sori are 1.0 to 1.5 mm in diameter, and spo- 

 rangia are 0.3 to 0.4 mm in diameter. The sporangia show an elongated indentation 

 on the lower abaxial side (shown in one sorus in text fig. 3A) . 



The trilete spores are subcircular to circular in equatorial outline (pi. 2, 

 figs. 4-10). Laesurae extend three-quarters the length of the spore radius and 



