GENUS TRILETES 



17 



the spinose lageniculate spores found in 

 earliest Chester and older rocks to bear dou- 

 ble or even ramifying processes. The earliest 

 such occurrence known from this study is 

 that of megaspores of T. crassiaculeatus, 

 each bearing only a few double-tipped 

 spines. Spinose lageniculate-type mega- 

 spores in older Mississippian deposits bear 

 such spines in increasing number and de- 

 gree of ramification. 



The coat of the spinose lageniculate 

 spores appears more or less punctate. 

 Wicher (1934a) in a description of Apicu- 

 lati-sporites latihirsutus (Triletes horri- 

 dus) noted that the surface is "sehr fein 

 netzforming bis punktiert." The coat some- 

 times appears very finely meshed and, in 

 this respect, is similar to the coat of some 

 fertile and abortive spores of Cystosporites 

 (especially C. verrucosus). 



Schopf (1938, p. 28) suggested that there 

 appears to be a progressive simplification of 

 the apical prominence during the Car- 

 boniferous. This seems to be more or less 

 true for the spinose spores of the section. 

 Among the smooth forms, spores of Triletes 

 levis (interpreted as T. nudus by some) oc- 

 cur in younger coal beds than do those of 

 T. rugosus and possess more highly devel- 

 oped apical prominences. Dijkstra (1958) 

 described some similar spores from Sigil- 

 lariostrobus cf. major. The relationship 

 of T. levis with the section Lagenicula may 

 be only apparent, however, because Lyco- 

 spora, usually associated with lageniculate 

 spores, is absent from coal beds containing 

 T. levis. It is probably unwise to segregate 

 the lageniculate spores as a distinct genus 

 until the relationship of spores of T. in- 

 dianensis, T. splendidus, T. globosus, T. 

 hirsutus, T. praetextus, and T. levis to the 

 spores typical of the section is understood 

 more clearly. 



The earliest occurrence of lageniculate 

 megaspores bearing double or forked spines 

 is in the older coals of the Chester Series. 

 The more commonly illustrated spinose 

 lageniculate spores are usually characteris- 

 tic of the Caseyville Group. Smooth lage- 

 niculate spores first occur in the Rock 

 Island (No. 1) and Murphysboro Coals, 



and arc present in the younger coals of the 

 Tradewater and Carbondale Groups. Those 

 with a highly developed apical prominence 

 appear to be restricted to coals of the Mc- 

 Leansboro Group. In this study, smooth 

 and spinose lageniculate spores have not 

 been observed together in the same sample. 



Triletes subpilosus (Ibrahim) Schopf, 



Wilson and Bentall, 1944 (sensu Dijkstra, 



1946) 



Plate 2, figures 1-5 



1933 Setosi-sporites subpilosus Ibrahim, p. 27; pi. 

 5; fig. 40. 



1944 Triletes subpilosus (Ibrahim) Schopf, Wil- 

 son, and Bentall, p. 26. 



1946 Triletes subpilosus (Ibrahim) Dijkstra, p. 

 46-47; pi. 11, figs. 116-128. 



1955 Lagenicula subpilosa (Ibrahim) Potoni£ and 

 Kremp, p. 120; pi. 4, fig. 21. 



Description. — Megaspores typical of spe- 

 cies of medium size, more or less bottle- 

 shaped, with distinct apical prominence, 

 generally compressed obliquely; maximum 

 equatorial diameter, measured perpendicu- 

 lar to the spore axis, from 550 to 1270 ^ 

 (mean 960 ^ for 25 specimens). Apical 

 prominence, measured from base of lips, 

 generally between 100 and 175 yu. in height, 

 up to 300 ix in width; lips thick, obscuring 

 suture, rarely open. Contact areas and lips, 

 especially area at base of lips, set with small 

 spines (pi. 2, fig. 1) generally about 5 ^ in 

 diameter and 5 ^ in height. 



Distal spore coat set with scattered spines 

 ranging from 56 to 128 ^ in maximum 

 length* and 10 to 30 ^ in width basally. 

 Spines more or less parallel-sided, usually 

 straight to gently recurved, and fluted bas- 

 ally, blunt to ball-tipped. Spines adjacent to 

 contact areas are shorter, more delicate, and 

 more crowded, but on some spores rather 

 widely spaced. No subsidiary distal spines 

 present. 



Spore coat punctate, 7 to 15/x thick, as 

 little as 4 /x thick on contact areas, yellow 

 to orange-brown by transmitted light. 



* Range in maximum length is the range of maxima observed 

 on all spores, not the minimum-maximum range in length. 

 This range of maxima is considered more meaningful because 

 spores of r everal species may c how comparable minima in spine 

 length. Therefore, in the species above, 56 (i is the shortest 

 maximum spine length ob erved on any spo:e; 120 fl is the 

 longest maximum length observed. 



