The Fossil Plants. 
171 
young stage united, but with age it splits along the 
line of the grooves between the ribs, and then every 
division becomes a long, narrow, strap-like leaf, joining 
a whorl round the transverse partitions. This genus 
has been noted in the Narrabeen Shales. 
Phyllotheca . — Sheath similar to Equisetum , but pro- 
longed into long linear leaves, usually like threads of 
wire, spreading in a whorl. 
“ Phyllotheca is at present little more than a generic 
name applied to jointed, and more or less costate, stems 
and branches, the latter springing from above the 
stem-joints, and bearing linear, verticillate leaves, with 
a central vein, free distally, but joined into a sheath 
proximally, and either erect or reflexed. As the name 
Phyllotheca was originally described from Australian 
material, it follows that the genus must derive its dis- 
tinctive characters from such, and whatever the fruc- 
tification eventually proves to be, so will foreign species 
fall within it, or be relegated to other genera.” 1 
Calamites . — Tree-like plants, with jointed cylindrical 
stems, and long strap-like leaves, longer than the 
branches. The Calamites are somewhat analogous to 
Equisetum , but the verticillate leaves are entirely free 
or confluent at their base. They had clusters of 
sporangia similar to Lycopods. This large genus of 
plants is subdivided into Calamocladus , C alamos- 
tachjjSy Huttonia , Macrostachya , and Bornia , which 
being minor distinctions need not occupy us here. 
Sphenophyllum . — Leaves in close whorls, wedge- 
1 R. Etheridge, Junr. Rec f Geol. Survey of N. S. Wales, Vol. IV., part 4. 
