On Spores in the Carboniferous Formation of Scotland. Ill 



Tkiletes XIIL PL IV., Figs. 13a, 135. 



Macrospore small. Triradiate ridge very prominent, and occu- 

 pying fully one-half of the upper surface. Surrounding area 

 of triradiate ridge smooth, or very obscurely apiculate. Other 

 portions of spore bear distant scattered stout short spines. 

 Only a few specimens of this form have been met with. 



Size. — 1*3 mm. 



Horizon. — Carboniferous Limestone Series. 



Locality. — 11. 



Division III.— Zonales. 



In this division are placed those Triletem on which the 

 supposed parasitic Stelidem occur. We have already ex- 

 pressed the opinion that the Stelidece (including Trichostelium 

 and Stichostelium) are integral parts of the spore on which 

 they occur. That this is the true explanation of the equa- 

 torial zones will be best seen from a comparison of the fossils 

 with some recent Lycopod macrospores. At Fig. 22a is given 

 an enlarged drawing of the upper view of a macrospore of 

 Selaginella caulescens. This spore is usually surrounded by 

 a solid and gently undulating equatorial zone, the triradiate 

 ridge extending from the centre of the spore to the border of 

 the zone, where it becomes slightly pointed, imparting to the 

 complete spore an obscurely triangular outline. Occasionally 

 a few spines are scattered on the surface of the spore. This 

 may be regarded as the normal form of the macrospore of 

 Selaginella caulescens. 



In this case it is quite impossible to do other than regard 

 the equatorial zone as an integral part of the spore. But 

 along with these solid-zoned macrospores a few others occur 

 having slits in the zone, as shown at Fig. 22h. This slitting is 

 sometimes carried further, when the zone in its inner part 

 becomes divided into a number of pedicel-like branches sup- 

 porting the peripheral portion, which may be solid or bear 

 one or two small perforations. 



If Triletes XVI., with its Stichostelian-Stelidece (PL V., 

 Fig. 16), is compared with the macrospores of Selaginella 

 caulescens, the one is seen to be an exact counterpart of the 



