32 



GROUP RELATIONSHIPS 



tion as to the reliability of specific dif- 

 ferences indicated by small-scale draw- 

 ings. Consequently these illustrations 

 are of little value in systematic study 

 of the spores. On the other hand, by 

 working with both the isolated spores 

 and the cones containing megaspores, 

 more satisfactory conclusions have been 

 reached. All compression - preserved 

 cones which are recognized as contain- 

 ing aphanozonate megaspores have been 

 identified by various earlier authors as 

 Sigillariostro'bus — not as the more com- 

 mon Lepidostro'bus. This does not mean 

 that all cones identified as Sigillariostro- 

 hws contained aphanozonate megaspores. 

 The case of S. sphenophylloides has been 

 discussed, and in several Sigillariostro- 

 l)ws species spores are not reported. 



It was not until the present study 

 was under way that it was realized that 

 the megaspores of Mazocarpon resem- 

 bled characteristic members of the apha- 

 nozonate section of Triletes (Schopf, 

 1938). The megaspores of M. oedipter- 

 7ium can easily be dissolved from the 

 coal-ball matrix by dilute hydrochloric 

 acid, and such spores display surface 

 characteristics somewhat better than the 

 spores obtained from nitric acid macera- 

 tion residues of coal. Arcuate ridges of 

 these spores dissolved from coal-balls 

 appear somewhat fainter than is usual 

 for Triletes reinschi. Spores similar to 

 these from M. oedipiernum but ob- 

 tained by ordinary maceration of coal 

 would probably be difficult or impos- 

 sible to distinguish from T. reinschi. 

 There is no question as to their close 

 relationship with that species although 

 uncertainty may exist as to their actual 

 identity. In a previous paper (Schopf 

 1938, p. 25) the probable relationship 

 of T. reinschi to several species as iden- 

 tified on the basis of cone characteristics 

 was pointed out. For example, spores 

 isolated from Sigillariostro'bus czar- 

 nockii would probably also be referred 

 to T. reinschi because the megaspore 

 coats in both instances possess similar 

 features. 



Apiculate members of Aphanozonati 

 (Triletes hrevispiculus) are only mod- 

 erately abundant in certain benches of 

 the Herrin (No. 6) coal bed in Illinois. 

 Coal maceration studies continued 



since 1938 indicate their rarity or ab- 

 sence from the greater part of the over- 

 lying Mcljeansboro. In lower Pennsyl- 

 vanian ' ' Pottsville " beds, apiculate 

 Aphanozonati are found more abun- 

 dantly, and the spines, which are the 

 chief means of differentiating species, 

 are more prominent. Triletes mamil- 

 larius Bartlett is of this group and 

 also many of those spores which Zerndt 

 (1934, pp. 17-18) has classified as type 

 14. These are all from beds of some 

 degree of stratigraphic coincidence, pos- 

 sibly falling in the lower and middle 

 Westphalian,! 1 (cf. text fig. 1 for ap- 

 proximate equivalence of stratigraphic 

 terms). The horizon from which Mazo- 

 carpon' shorense was derived belongs in 

 lower Westphalian A. The megaspores 

 from this cone are also prominently 

 apiculate. From the illustrations given, 

 one cannot tell much about the type of 

 ornamentation of M. shorense mega- 

 spores because all are from sections. 

 One may hope that a full description 

 of the English Mazocarpon spores will 

 be provided, as a good description is 

 unavailable at present. In view of the 

 agreement in the forms obtained in sec- 

 tions with those in sections from cones 

 of M. oedipternum, there can be no doubt 

 that the M. shorense megaspores fall in 

 the aphanozonate section of the genus 

 Triletes along with megaspores of the 

 type known from Sigillariostro'bus cili- 

 atus, S. rhombihracteatus, S. czarnockii, 

 S. tieghenii (cf. illustrations in Kidston, 

 1897; Zeiller, 1884, etc.) and the others 

 which have been discussed. This agree- 

 ment, in the opinion of the writer, is 

 one of the strongest reasons for consid- 

 ering Mazocarpon and Sigillariostrobus 

 to be closely related. The number of 

 megaspores in sporangia in the two 

 groups is not necessarily discordant. 

 They are not very numerous in spor- 

 angia of any species of Sigillariostrobus 

 although the numbers in individual 

 sporangia cannot be established with 

 the same accuracy as in petrified ma- 

 terial of Mazocarpon. 



It is evident from the preceding dis- 

 cussion that biological criteria distin- 



"Zerndt, 1940, p. 143, indicates that his type 

 14 spores extend through the Westphalian D, but 

 are not found in the Stephanian. 



