136 CANADIAN. FOSSILS. 
Grenus DICTYONEMA, Hall.. 
Gr. Sixrvoy, rete, and ynua, filum. 
(Dictyonema, Pal. N. Y., vol. ii, p. 174, 1852, and Geol. Survey of Canada, Report for 
1857, p. 142. Grapropora, Salter, Proc. Amer. Assoc.; Montreal, 1857.) 
Generic characters.—Fronds consisting of flabelliform or funnel-shaped 
expansions (circular from compression), composed of slender radiating 
branches, which frequently bifurcate as they recede from the base. 
Branches and subdivisions united laterally by fine transverse dissepiments ; 
exterior of branches strongly striated and often deeply indented; inner 
surface celluliferous or serrate, as in Graptolithus. 
The general aspect of the species of this genus is like that of Fenestella, 
both in the form of the fronds and bifurcation of the branches. . Some of 
the species have heretofore been referred to that genus, and others to 
Gorgonia. They may be known from either of these genera by the striated 
and serrated corneous skeleton, and by the absence of round cellules ; which 
latter character, with a calcareous frond, marks /enestella. 
oe 
DICTYONEMA IRREGULARIS, Hall. (a. s.) 
Plate XX, figures 1, 2. 
Deseription.—Frond spreading, diffuse. Branches lax, frequently bifur- 
cating; bifurcations unequal ; branches equal to one half the usual width of 
the interspaces, or a little less ; connecting filaments generally slender, ex- 
panding at their junction with the branches. Fenestrules extremely irregular 
in form and proportions, varying from a width greater than the length, to 
a length three or four times as great as the width; those with a length and 
breadth nearly equal, often appear hexagonal. Near the base of the frond, 
the fenestrules are sometimes elongate and triangular. Cellules unde- 
termined. Surface without distinct organic markmgs. Branches arranged 
in the proportion of from twenty-five to twenty-eight in the space of an 
inch. 
This species is much smaller than either of the others, scarcely equalling 
in dimensions the D. gracilis of the Niagara group, from which it differs 
in its more irregular form and diffuse habit. In one specimen there 
appear to be some identations upon the stone, indicating minute cellules, 
but they are too obscure for satisfactory determination. This species has 
been seen only in small fragments: the entire frond is unknown. 
