114 CANADIAN FOSSILS. 
Canadian species I have not been able to discover a reticulate structure 
similar to the European species, nor like that from the Clinton group of New 
York ; but there is sometimes an apparent punctate texture, and the test 
is thickened. Although the axis and cell-divisions are usually distinctly 
visible, they have not the characters of Diplograptus. 
The R. Geinitzianus of Barrande is found in Bohemia and Saxony at the 
base of the Upper Silurian, and probably not far from the same horizon as 
the American species ft. venosus. 
The R. ensiformis of the Quebec group holds a much lower geo- 
logical position, which, together with the difference of structure, leads me 
to suppose that it may ultimately be separated as a distinct genus. 
RETIOLITES ENSIFORMIS, Hall. 
Plate XIV, figures 1-5. 
(GRAPTOLITHUS ENSIFORMIS, Hall: Geological Survey of Canada, Report for 1850, p. 133.) 
Description.—Stipe simple, sub-ensiform or elongate-lanceolate, usually 
broader in the middle and narrower towards the extremities: axis central, 
with strongly-marked obliquely ascending striz reaching to the margins. 
Cellules obscure, apparently corresponding to the striz ; margin usually 
well defined. Width of stipe, in the largest individuals, sixteen hundredths 
of an inch ; length nearly two and a half inches. Other specimens have a 
width of one twentieth of an inch, with a length of half an inch. Cellules 
about twenty-eight in the space of an inch, inclined to the axis at an angle 
of about 50°, and without any appreciable portion being free. The solid 
axis is slightly undulating, and the cell-partitions alternate on the two sides 
of it, thus separating the cellules from each other. In some specimens the 
base is rounded and obtuse; others show a continuation of the axis, or a 
central straight radicle. Substance of the test punctate. 
All the specimens are extremely flattened, and it is very difficult to 
distinguish any difference in the opposite sides of individuals. In the best- 
defined specimen there is a distinct axis with alternate diverging filaments 
or cell-divisions, which reach to the outer margin, the substance being nearly 
all removed except this skeleton. In a single specimen, the axis is not 
strictly defined, and is broader, while the diverging partitions are less 
strongly marked. This one affords the only evidence that we have of the 
difference in the two sides of the species, a difference shown in the 
R. Geinitzianus of Barrande. 
