GENUS TRILETES 



29 



cording to Chaloner [1953c]), originally 

 saucer-shaped, generally proximo-distally 

 compressed. Spore diameter ranging from 

 935 to 2270^ (mean 1600 p for 37 wet or 

 balsam-mounted specimens). Spore diam- 

 eter of dry specimens (text fig. 3) from 625 

 to 1520 fx (mean 1155 /x for 11 specimens). 

 Trilete rays generally low, ranging in length 

 from one-third to two-thirds spore radius, 

 sometimes possessing an apical expansion 

 up to 93 /jL in height. Suture may be open, 

 generally throughout half its length. 



Contact areas ornamented by spines from 

 2.5 to 25 fx in diameter and from 2.5 to 28 ^ 

 in height, smallest near apex. Distal spines 

 with expanded bases and pointed tips, 

 closely spaced, from 20 to 94 ^ in diameter 

 basally and from 31 to 130 ^ in length. 

 Spore coat from 21 to 36 ^ thick on mature 

 spores, from 36 to 62 fx on immature spores; 

 coat brown to black by reflected light, deep 

 reddish brown by transmitted light. 



Discussion. — The description given above 

 is that of the megaspores from the Willis 

 Coal because this species is most abundant- 

 ly represented in this coal, with the excep- 

 tion possibly of Herrin (No. 6) Coal. Those 

 found in the Caseyville Group from the 

 coals of the Wabash County cores (pi. 7, 

 figs. 6a, 6b) range from 880 to 1965 /x in 

 diameter. Distal spines range from 15 to 

 113/x in diameter and from 25 to 100^ in 

 length. All spores have spinose contact 

 areas. Those of the Herrin (No. 6) Coal 

 are generally about 1900 ^ in diameter or 

 less and possess distal spines up to 15 ^ in 

 height. Although spores referable to this 

 species (s.l.) have been recognized from 

 Caseyville, Tradewater, and Carbondale 

 coals, only a few specimens from coals other 

 than the Herrin (No. 6) Coal possess the 

 extremely small apiculi described by Schopf 

 (1938) for Triletes brevispi cuius. 



Chaloner (1953c) described Triletes 

 rnamillarius-type megaspores from cones of 

 Sigillariostrobus and noted a wide range of 

 variation in spine development. However, 

 he noted that no spines are as small as 

 those described by Schopf (1938) for T. 

 brevispiculus (included in T. mamillarius 

 by Dijkstra, 1946) or as slender as those de- 



scribed by Arnold (1950) for T. fermi. The 

 spore variation in two species substantiates 

 the variety of types included in T. mamil- 

 larius by Dijkstra. 



According to Dijkstra (1955a) spores of 

 this species occur in the Namunan A — 

 Westphalian C in Poland, in the West- 

 phahan A-D in Turkey, and up to the 

 Westphalian D in Bohemia and in the Saar 

 Basin. 



Occurrence. — Spores of this species are 

 present in the Jagger, Newcastle, Gillespie, 

 America, and Pratt Coals of the Warrior 

 Basin; they are particularly abundant in 

 the Jagger and Pratt Coals. The species 

 also is represented in the French Lick Coal 

 (maceration 151) and in the shale (macer- 

 ation 163) above the Pinnick Coal in Indi- 

 ana. 



The spores are common in the older coals 

 of the Caseyville Group (macerations 796, 

 795, 798). In the Tradewater Group they 

 are present in the Babylon Coal (macera- 

 tion 588); common to abundant in the 

 Willis Coal (macerations 625, 631); rare in 

 the Pope Creek (macerations 916, 602), 

 Rock Island (No. 1) (macerations 929, 589), 

 Murphysboro (macerations 915, 628B), un- 

 named coal bed above DeKoven (macera- 

 tion 35), DeKoven (?) (maceration 62 ID) 

 Coals, and in the lower coal from Goose 

 Lake (maceration 950A); common in the 

 Wiley Coal (maceration 525B). 



In the Carbondale Group the spores are 

 rare to present in the Colchester (No. 2) 

 Coal (maceration 603C) , Summum (No. 4) 

 Coal (maceration 463), and Springfield 

 (No. 5) (maceration 630) Coal. The spores 

 are moderately abundant in the Herrin 

 (No. 6) Coal (Schopf, 1938). As yet, the 

 species is not known to be represented in 

 younger coals. 



Sectio Auriculati Schopf, 1938 



Spores of the Auriculati section of Tri- 

 letes are of medium size, subtriangular to 

 trilobate in outline. Trilete rays long, usu- 

 ally extending to equator. Lobate expan- 

 sions of spore coat sometimes developed at 

 radial extremities. Interradially a flange or 



