EARLY PENNSYLVANIA FLORA FROM WEST-CENTRAL ILLINOIS 37 



the latter being 0.5 mm to 1.0 mm vide on the sides, thicker at the apex 

 and thinner at the base. In some instances the nucellus, as is the sur- 

 rounding sclerotesta, is preserved only as a thin, flattened carbon film. 

 In other cases, the nucellus is preserved in three-dimensional form and 

 is about 1 to 2 mm thick. Such differences are probably preservational 

 and make comparison of specimens difficult. These specimens bear a 

 strong resemblance to Cardiocarpon late-alatum Lesquereux. 



PROBLEMATICA 



The Spencer Farm Flora contains a number of fragmentary speci- 

 mens that do not belong to any of the species described above. They 

 are too incompletely preserved to be identified with any degree of con- 

 fidence. However, these fragments may be recognizable if more material 

 becomes available from here or other locations. Therefore, we include 

 short descriptions and figures. 



Specimens ISM kl63Q0 and ISM kl62^>8 (text fig. 121; pi. 5, fig. 

 5; pi. lk 9 figs. k 9 5) are Sphenopteris- or Afariopteris-like. The pin- 

 nules are subtriangular to triangular to lanceolate with an only slightly 

 lobed margin on the largest pinnule. The pinnules are arranged obliquely 

 and alternately on the pinna rachis. The pinnules are decurrent, but 

 the base is constricted slightly on the lower side, more so on the upper. 

 The nervation of the two specimens is indistinct; the midvein originates 

 at an acute angle and arches outward. The veinlets divide at least once 

 as they curve outward to the margin. The measurements are: 



ISM U16258 ISM U16380 



pinnule length (mm) 9, 12, lk 9 12+, Ik 6, 7 



pinnule width (mm) k 9 h 9 k.5 9 U.5, U.5 2, 3, 3 



Another specimen, ISM Ul6529 (text fig. 12G, H; pi. 5, fig. 6), 

 is an Eremopteris-1 ike form. It has an alated rachis; pinnules are al- 

 ternate and overlapping. The pinnule bases are very narrow and decur- 

 rent. The pinnules are deeply trilobed, and each lobe is further dis- 

 tinctly subdivided, each sublobe being either linear or slightly tri- 

 angular . 



It appears that a single vein enters each pinnule and divides 

 one or two times to give rise to two or three nearly parallel veins in 

 each lobe. 



DISCUSSION 



The Spencer Farm Flora is remarkable with respect to its mode of 

 occurrence and the taxa present. The flora did not grow in a coal-form- 

 ing environment, and the differences between this flora and normal roof- 

 shale floras are thus in part due to the environmental differences. 

 White (1931) was the first to point out that the basal Pennsylvanian 

 floras of this kind were growing on the limestone plains and hills in 

 western Illinois in early Pennsylvanian time. Leary (197^+a, 197 Vb) gave 



