protrusion, archegonia are formed on the prothallus. 
All of the gametophytic stages preserved in the fos- 
sil strobilus from Illinois are intermediate between the 
earliest nuclear divisions of the megaspore and the open- 
ing of the spore wall. No protruding gametophytes have 
been observed in more than 1500 sections representing 
more than 200 megaspores. No archegonia have been ob- 
served, presumably because they would have been borne 
upon the protruding portions of the gametophytes. 
Description of the species. 
Selaginella Amesiana Darrah sp. nov. 7 figures. 
The strobilus is composed of spirally disposed meg- 
asporangia each bearing four megaspores. The mega- 
spores were ornamented by a reticulate exospore and by 
a well developed equatorial flange. ‘The female gameto- 
phyte was constructed of angular and somewhat elongate 
parenchymatous cells with nuclei and nucleoli preserved. 
Its development was endosporal. 
The strobilus (as much as is preserved) measures 27 
mm. in length and 3.5 mm. at the maximum width. The 
megaspores have a diameter of 750 micra including the 
equatorial flange, and a height of 450 micra. 
Foliage, ligule, microspores, microsporangia, and 
archegonia are not known. 
I have the pleasure of naming this species for Pro- 
fessor Oakes Ames, Director of the Botanical Museum 
of Harvard University, for his continued interest in pale- 
obotany and for his enthusiastic support and encourage- 
ment of the activities of our Paleobotanical Laboratory. 
Discussion of Relationships. 
The megagametophyte of Selaginella A mesiana may 
be compared with the prothalli of Bothrodendron mun- 
dum and Lepidodendron Veltheimianus. 
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