40 T. G. HALLE, MESOZOIC DEPOSITS AND FLORAS OF PATAGONIA AND TIERRA DEL FUEGO. 
Arthrotaxites Ungeri n. sp. 
PI. "2; figs; 11—17; pl. 3, figs. 13—20, 212: pl 4, fig. 225 pl. 5, hest f0=T3: 
Most of the coniferous remains in the San Martin flora appear to belong to one 
species, which has been referred here to the genus Arthrotaxites UNGER. 
Sterile shoots sparsely branched, slender, covered with spirally disposed, closely 
adpressed, ovate-rhombic leaves, which cause the surface of the branch to appear 
divided up into regular rhombic areoles. The slenderest twigs with the leaves less 
closely adpressed and somewhat more lanceolate. Cones globular, 10—15 mm. in 
diameter, carried on rather thick (often?) curved branches. Cone-scales densely placed, 
with a cuneate base and a thick, spatulate upper portion, prolonged into a short 
acumen, which is distinetly marked off from the rest of the thick apical expansion 
of the scale. 
Sterile fragments of this species abound in many specimens of the plant-bearing 
rock. No very thick branches can be identified, however, probably because the leaves 
tend to become indistincet in the thick specimens. The thickest branches with pre- 
served leaves do not generally exceed 3 mm. in breadth on the impressions. In pl. 
2, figs. 11 and 12, the thickest branches identified are shown. There is some little 
variation in regard to the leaves, mostly expressed in the different closeness of their 
application to the stem. In typical specimens the leaves always cover the stem so 
closely that they appear to form a regular network of areoles on its surface. They 
have in these specimens rhombic outlines, with straight edges and acute but not 
sharply pointed apices. Some such typical branches are seen in pl. 2, figs. 13 and 
14, and in magnification in figs. 15—17. In other specimens, especially in slender 
ones, the application of the leaves is a little laxer, and in such cases they are often 
somewhat different, being more convex and more ovate-lanceolate. 
There can hardly be any doubt that the cones to be described in this connec- 
tion really belong to the same species. The cones are frequent, but usually occur 
detached from the stems. In single cases, however, they are still attached to short 
branches, so for instance those in pl. 3, fig. 14 and pl. 5, fig. 10. The supporting 
branch measures in these specimens only about 1,5 cm. in length and is strongly 
curved. In none of these specimens are the leaves distinct, yet the resemblance to 
the common type of sterile shoots is so obvious that the attribution appears safe. 
Besides, the fact that the cones and the sterile branches are the only common coni- 
ferous remains in the rock and remarkably often occur in the same specimens of it, 
tends to confirm this opinion concerning their connection. The cones appear to have 
been globular: the impressions are more or less circular measuring about 10—15 mm. 
in diameter. The cone-scales have evidently been rather thick. As seen from the 
surface they are somewhat spatulate, their lower petiolar part being rather long and 
gradually widening towards the broader and thicker upper portion. The latter has 
an abruptly tapered but not truncate apex, prolonged into a sharp and marked point. 
