46 CANADIAN FOSSILS. 
simple undivided part of the stipe. Moreover, the species is recognized 
in this condition m the Hudson River formation in Canada, and has like- 
wise been recognized in Great Britain ; while a similar or identical form 
has-been shown by Prof. McCoy to occur in Australia. We must there- 
fore seek some other than an accidental cause for the explanation of this 
uniform bifurcation of the stipes of that species. In the meantime, it 
appears to me highly proper to suggest its separation from Diplograptus. 
On farther comparison, we shall find that G'. ramosus is not quite alone 
in its peculiar characters. In G. furcatus there are a few cellules at the 
base of a simple stipe below its bifurcation ; and in G. sextans, the lower 
part of the stipe is simple, the division taking place above the first cellule ; 
but in entire individuals the division is never from the initial point, as we 
see it in G. bifidus and G. nitidus of this memoir. 
Now these first-named species, as well as G. ramosus, have cellules of a 
peculiar form ; and looking still farther, we find a similar form of cellule in 
G. Lorchhammert, Geinitz, and G. divaricatus, Hall, two species which are 
divided from the base, having a single range of cellules upon the outer 
sides of the stipe. I believe it will be found, moreover, that all the 
graptolites with cellules on the lower side of the stipes (in reference to 
the initial point or radicle) have these parts of the same form as G. ramosus, 
and very unlike the G. pristis and allied species. Nor are the cellules 
on the simple or divided portions of the same stipe, or on those which are 
entirely divided and upon the lower side, at all like the cellules of G. priodon, - 
G. geminus, G. Murchison, or any of the allied forms illustrated in this 
memoir, to which the term Didymograptus has been applied ; nor can they 
be properly united with them. ‘The form of the cellules is always suffi- 
ciently distinctive even in fragments of the stipes; and this feature, together 
with the mode of development or growth, seems to me sufficient to sustam a 
generic distinction. 
The genus /tetiolites is described by M. Barrande as having no central 
solid axis, but with a single internal canal occupying the median portion 
of the polyp. The prevailing form of the stipe is somewhat concayvo- 
convex, with the centre of the concave side prominent; the entire surface. 
is covered by a net-work of corneous substance, and the cell-apertures 
are quadrangular. 
Prof. Geinitz has given some further illustrations, showing more em- 
phatically a longitudinal axis on the convex side, to which are joined the 
ceell-partitions ; while he regards the common body as occupying the 
prominent central portion of the concave face of the stipe, and shows 
the cell-partitions terminating before reaching the centre, leaving a space 
occupied by the width of the common body. This he represents as covered 
by a net-work of slightly different texture from that of the other portions 
of the substance. 
