900 FLOKAL ZONES OF THE POTTSVILLE FORMATION. 



of Sjphenojjliylhim emarginatum. It exhibits the more rigid type of 

 leaf, with the coarse nervation of tlie latter, to which the Pottsville 

 form appears to stand in an antecedent relation. The leaves of the 

 first t3'pe, which is more typical of the horizon of the Sewell-Sewanee 

 coal, or Lvkens coals Xos. 2 and 3, in the Southern Anthracite field, 

 are relatively rarely dissected, while those of the second or more rigid 

 type, which occurs in the Upper Intermediate division in the anthracite 

 region, are nearh' always unevenly dissected. 



Sphenophyllum tenue sp. nov. 



PI. CXCl, Figs. 6, T. 



Stems slender, distinctly though not very prominently ribbed, cari- 

 nate, 1 to 3 mm. in diameter, branching a little freely, the branches, 

 often in verticils of three, springing from within the bases of verticils 

 of very deeply dissected leaves; nodes distinct, 1 to 5 cm. distant, 

 usually having the leaves still attached; leaves in verticils of six, 

 oblique at the base, very rapidly spread In nearh^ equidistant radia- 

 tion, broadly cuneate, 1 to 2 cm. in length, usually about 8 mm. in 

 width, very thin or membranous, lax, the apices round-truncate, 

 more rounded near the angles, sometimes with a faint sinus at the cen- 

 ter, crenulo-denticulate in 12 to 2-J: short, broad, round-obtuse teeth, 

 or rarely more or less dissected in broad, \ev\ lax, obtuse, usually bi 

 or tri dentate laminae, the lateral margins distinctly, sometimes rather 

 strongly, concave and converging downward in a slender, very narrow, 

 relatively long, slightly thickened base; primary nerve single and 

 rather strong for some distance in the lower part of the leaf, forking 

 four or five times at a slightly narrow angle in passing upward, slen- 

 der and delicate, to furnish one nerville for each tooth or denticulate 

 crenulation. 



The salient features of this species are the large, membranous, very 

 broadly cuneate, crenulate-denticulate. slightly rounded leaves, with 

 distinctly il: not conspicuously concave lateral margins and long slen- 

 der bases, in verticils of six, on ver}^ slender stems. The aspect of 

 the somewhat rounded, rarely sinused apex, the transparent lamina, 

 and the narrow, slender bases, below such l)road apices, make the plant 

 easily recognizable among the other species of its genus. The nerva- 

 tion is thin and delicate, derived In' numerous bifurcations from a 

 rather thick, single, primary bundle that passes for some di.-tance 

 throuji'h the narrow base of the leaf before dividing. Leaves " the 

 dissected type, such as that shown in PI. CXCI, Fig. 7, are more rare. 

 Although they bear a closer resemblance to the laciniate forms of other 

 large-leafed species, th6y are easily distinguished by the irregular, 

 very broad, obtuse, and lax type of the lacinea\ which show a markedly 

 broad spread at the top, and b}- the concave lateral profile and the 



