from the Quebec Group of Point Livis. 



135 



and often curved, with their convexities directed towards the 

 base of the frond. Cellules undetermined. Surface smooth. 

 Length of the largest frond observed (not a perfect one) a little 

 over two inches, breadth a little above the base about one fifth 

 of an inch, breadth at summit nearly two inches (fig. 1, a, 6). 



Fig. 1. 



ft « «^ Z! -» ' ? X »J 





^0.11n^ 



Ml, 



^r,ifi 



^VffVfff 



'1^ 



Dictyonema grnndls, Nich. : a, fragment of a frond, natural size, showing 

 the rapid divergence and bifurcation of the branches ; b, a fragment, 

 enlarged, to show the fenestrules and connecting filaments. 



There can be no doubt as to the close alliance which subsists 

 between this species and the Dictyonema Murrayi described by 

 Hall from the shales of Point Levis (Grapt. Quebec Group, 

 p. 138, pi. XX. figs. 6, 7). The following are the characters 

 ascribed to the latter : — "Frond very large, gi-adually spreading 

 from its origin. Branches strong, width from 5 to 8 hundredths 

 of an inch, infrequently bifurcating ; divisions little diverging, 

 the interspaces being little wider than the branches. The 

 fenestrules have a width of 8 by a length of 11 hundredths of 

 an inch. The connecting filaments are wide at their origin or 

 union with the branch, and slender in the middle ; from about 

 one third to one half as wide as the branches. Cellules un- 

 determined. Surface smooth." 



When we compare the above description with that of the 

 present species, the latter appears to be clearly separated by 

 the conical form of the frond, and the rapid divergence and 

 frequent bifurcation of the branches, whilst the fenestrules are 

 almost always markedly wider than they are long, the reverse 

 of this obtaining in D. Murrayi. Tliese peculiarities along 

 with some other, minor differences, which will be sufficiently 



