42 



ILLINOIS STATE GEOLOGICAL SURVEY 



tubercles rather than spinose ornamenta- 

 tion. The ornament does not seem to be a 

 relict of spinose ornamentation caused by 

 abrasion. In general, among four of the five 

 T. globosus— T. hirsutus type of megaspores 

 here distinguished there is, from older to 

 younger rocks, a slight increase in spore 

 coat thickness and there are changes from 

 short to long catenulate spines, to short 

 discrete shallowly cleft spines, to longer 

 more ramose spines. Zerndt (1937a) noted 

 somewhat similar changes, from older to 

 younger specimens, on spores of this gen- 

 eral type. 



Probably all of the megaspores, generally 

 poorly preserved, of the Triletes globosus- 

 type found in the Jefferson (rare) , Middle 

 Ream, Jagger, and Pratt Coals of the War- 

 rior Basin, Alabama, can be referred to T. 

 globosus var. (B) . This varietal form is 

 typically developed and beautifully pre- 

 served in the lowest coal in a diamond drill 

 core from Wabash County (maceration 

 798) and in the shale above the Pinnick 

 Coal (maceration 163) in Indiana, but 

 abraded and not as well preserved in the 

 upper coals of the diamond drill cores from 

 Wabash County (macerations 796, 797) 

 and Battery Rock Coal (maceration 587) . 

 Characteristic of Caseyville coals is the 

 abundance of typical T. globosus spores or 

 those of T. globosus var. (B) . 



In contrast to the above spores, those of 

 Triletes praetextus seem to be restricted to 

 the Battery Rock Coal in Illinois, to the 

 shale above the Pinnick Coal in Indiana, 

 and to the Pratt Coal in Alabama. How- 

 ever, in the latter two areas no immediately 

 overlying coals were examined. Although 

 spores described here appear identical to 

 those previously described from European 

 coals, T. praetextus in European coals is 

 apparently much more abundant and has a 

 more extended stratigraphic range. 



Triletes globosus Arnold, 1950 



Plate 5, figures 1-6 



1950 Triletes globosus Arnold, p. 80-81; pi. IX, 

 figs. 1-5. 



Description. — Megaspores typical of spe- 

 cies trilete, usually compressed proximo- 



distally, more or less circular in outline 

 (pi. 5, fig. 1), from 385 to 640 ^ in diameter 

 (mean 535 ^ for 27 specimens) . Trilete 

 rays distinct, ranging in length from two- 

 thirds to three-fourths the spore body ra- 

 dius. Lips increasing in height abruptly 

 near apex to form an apical prominence 

 (pi. 5, fig. 4) up to 75 fx in height. Contact 

 areas, occasionally even lips, characterized 

 by rather closely spaced acuminate spines 

 up to 5 fx, both in height and diameter. 



Distal spines typically discrete, peglike 

 (pi. 5, fig. 2) , ranging from 26 to 61 ^ in 

 maximum length on different spores, ter- 

 minating in an expanded, slightly cleft (pi. 

 5, fig. 2) or barbed (pi. 5, figs. 3, 5) tip. 



Distal spore coat ranging from 1 3 to 28 ^, 

 generally more than 20 ^ in thickness, 

 orange-brown to reddish brown by trans- 

 mitted light. A folded inner membrane is 

 inside the spore body of many specimens. 



Discussion. — These typical spores of Tri- 

 letes globosus are differentiated from the 

 varietal forms described below in that they 

 possess comparatively widely spaced, dis- 

 crete, peglike spines with characteristic 

 terminal barbs. The spine terminations are 

 cleft to a depth of commonly less than 12 jx, 

 not deeply cleft nor anastomosing and 

 branching as on spores typical of T. hir- 

 sutus (Loose) Schopf, Wilson, and Bentall. 



These spores are very similar to those 

 originally described by Arnold although 

 none was observed to have an apex as high 

 as 110/x. All but a few examples observed 

 during this study have a characteristically 

 apiculate contact area. Although Arnold 

 did not note this contact area ornamenta- 

 tion, distinguishable with difficulty in 

 proximo-distal compressions, one specimen 

 that he illustrated (Arnold, 1950, pi. IX, 

 fig.l) appears to be similarly ornamented. 

 The spores Arnold described were from the 

 shale from the Big Chief No. 8 Mine at 

 St. Charles, Michigan. 



Occurrence. — Triletes globosus is abun- 

 dantly represented in Caseyville coals of 

 Illinois, especially in the Reynoldsburg 

 Coal (maceration 618) , the Battery Rock 

 Coal (macerations 629, 908, 909) , and the 

 "Makanda" Coal (macerations 906, 907). 

 A few additional examples also are pres- 



