Silurian.] PALZONTOLOGY OF VICTORIA. [ Graptolites, 
PratE XX., Fia. 1. 
GRAPTOLITES (DIDYMOGRAPSUS) EXTENSUS (Hatt). 
[Genus GRAPTOLITES (Lim.). (Class Zoophyta, Order Hydrozoa. Fam. Graptolitide), 
Gen. Char.—Polypidom horny, elongate, compressed, with a slender solid axis along one 
edge, followed by a parallel common longitudinal canal, from which one close row of cells 
extends, each inclined upwards and outwards, and all terminating in separate apertures on the 
serrated edge opposite the solid axis, 
Sub-genera.—1, Graptolites (proper). Stem single and simple; Upper and Lower Silurian. 
—2. Didymograpsus (McCoy). Stems simple, but united in groups of two or more by the 
pointed uncelled lower end. Some of these have a round horny dise connecting the non- 
celluliferous bases of the grouped stems ; Lower Silurian. Some writers divide the species into 
sub-genera Tetragraptus, Loganograptus, &c., according to the number of stems conjoined, a 
character certainly not of generic value]. 
DescriptTion.—Radicle forming a very small acute point, scarcely a line long, 
from which the two stems extend nearly at right angles and nearly in one straight 
line, and in the same plane right and left to a length usually of upwards of 8 inches, 
and a width of about ? of a line at 2 inches from the radicle; the cells are on the 
ope side, acutely angular, the space of three cell points about equalling the width 
of the stem from cell points to back; and the breadth of the top of the cell or 
indentation equals about 4 of the width of the stem, the outer line of each cell 
making an angle of about 42° with the back, about seven cells in 8 lines. 
REFERENCE.—(Hall), Grap. Can., t. 2., f. 11 to 16. 
The closer cell-teeth, when compared with the width of the 
stem, seem to separate this from the New York Graptolites serra- 
tulus. None of our stems are quite so wide as the Canadian 
examples of the G. extensus, but I do not think there can be 
any reasonable doubt of their specific identity. 
Occurs in great abundance in the black Llandeilo flags of B* 1, 
branch of Parman Creek, 4 miles N. of Gvriffiths and Green’s 
Station. . 
EXPLANATION OF FIGURES. 
_ Plate XX.—Fig. 1, rather small specimen, natural size, the branches imperfect at each end. 
Fig. 1a, portion of ditto magnified, but with the cell-teeth slightly too erect and a little too 
deeply indented, 
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