GENUS TRILETES 



19 



mens). Apical prominence rather triangu- 

 lar in lateral outline (pi. 1, figs. 6, 8), from 

 125 to 340 fx in height from base of lips, usu- 

 ally less than 200 p.. Lips rather thick, ob- 

 scuring suture, rarely open. Trilete rays 

 equalling about one-third the radius of the 

 spore body; contact areas occupying about 

 two-fifths the proximal hemisphere. Con- 

 tact areas and lips, especially area at base of 

 lips, generally heavily ornamented with 

 small pointed spines 10 to 20^ in length 

 and up to 10 ^ in width. 



Closely spaced distal spines from 90 to 

 340 n in maximum length, 10 to 30 /x in 

 width basally. Spines more or less parallel- 

 sided, extending outward from a fluted, 

 hollow-appearing base to a blunt, pointed, 

 or ball- to cup-shaped tip. Spines straight, 

 sinuous, or gently refiexed; some appear 

 ribbon-like (pi. 1, fig. 3), never forked. 

 Spines generally more delicate, crowded, 

 and about one-half the length of the distal 

 spines at the margins of the contact area. 

 No small subsidiary distal spines present. 



Spore coat punctate or minutely meshed, 

 7 to 20 n thick, thinnest in the contact areas, 

 generally yellow to orange-brown by trans- 

 mitted light. 



Discussion. — These spores are abundant 

 in and characteristic of Chester age rocks. 

 The small gradual decreases in total size, 

 spine length, and spore coat thickness from 

 oldest Chester to youngest Chester age meg- 

 aspores are not considered adequately de- 

 lineated at this time for taxonomic separa- 

 tion. The spores of the four samples, upon 

 which most of the measurements were 

 made, seem to tall into two more or less dis- 

 tinct groups within Triletes subpilosas 

 forma major. Those from the Degonia 

 (maceration 143) and Hardinsburg (mac- 

 eration 166) Formations of Illinois have 

 comparable mean diameters of 1015 /x (5 

 spores) and 970 /x (19 spores) with maxi- 

 mum diameters of 1270 ^ and 1240 jX respec- 

 tively. 



In contrast, spores from a coal in the 

 Hardinsburg Formation (maceration 810) 

 and from a coal in Bethel (Mooretown) 

 Formation (maceration 943) of Kentucky 

 have comparable mean diameters of 1315 /x 



(19 spores) and 1295 /x (31 spores) with 

 maximum diameters of 1695 fx and 1790 p.. 

 More than half of the spores from the coal 

 in the Bethel (Mooretown) Formation pos- 

 sess spines having a maximum length of 

 more than 200 /x; one spore has spines up to 

 340 xt in length. In addition, spore coat 

 thickness exceeds 15 to 16/x only in this 

 older coal. 



All these spores have certain charactens 

 tic features in common, also shared by the 

 younger megaspores typical of the species. 

 These features are the rather stunted-ap- 

 pearing apical prominence, at least less ex- 

 panded than that on spores of Triletes hor- 

 rid us; a usually heavy ornamentation of 

 contact areas and lips; more or less par- 

 allel-sided spines, blunt to ball-tipped and 

 fluted basally; the absence of small subsid- 

 iary distal spines. 



The spores of macerations 143 and 166 

 are somewhat smaller than those described 

 as Triletes subpilosus forma major by Chal- 

 oner (1954b) from the Beaver Bend Lime- 

 stone of Indiana. They are approximately 

 the same size as, but with a thinner spore 

 coat than, those described as T. cf. T. sub- 

 pilosus forma major by Dijkstra (1957) 

 from the Namurian of Scotland. However, 

 the spine length and spore coat thickness 

 of the latter are comparable with those of 

 spores from the older Chester formations. 

 These older spores are probably identical 

 to those Chaloner describes from the Bea- 

 ver Bend Limestone but have more exten- 

 sive size limits. The other megaspores, of 

 probable Kinderhook age, that Chaloner 

 describes as T. subpilosus forma major are 

 not characteristic of this species. 



Spores of Triletes subpilosus forma major 

 in the lower part of the Chester bear some 

 similarities to megaspores of T. crassiacu- 

 leatus with which they may occur. How- 

 ever, spores of T. subpilosus forma major 

 are smaller, do not have the tall, expanded, 

 apical prominence, lack subsidiary distal 

 spines and forked spines, and have a thin- 

 ner spore coat. 



Most of the spine tip features described 

 by Bennie and Kidston (1886) are found on 

 spores of Triletes subpilosus forma major. 



