48 CANADIAN FOSSILS. 
The species for which I have proposed the genus Phyllograptus, pre- 
sent close analogies with the typical form of Diplograptus in the character 
of test and form of cellules. These, in their aperture and form, are nearly 
quadrangular; and the cell-partitions are apparently continuous between 
the cellules, and reach nearly to the central axis ; characters which we find 
in Diplograptus. These forms, in their great lateral extension, depart 
widely from their analogues; but they differ more essentially in their 
cruciform mode of growth, presenting an arrangement of parts, as if four 
simple stipes (like those of G. bryonoides or G. Bigsbyi) were joined 
together by the coalescing of the solid axes. In this latter respect, and 
in their great development in width, they differ most essentially from 
all the other genera of this family of fossils. ‘These forms are fully 
illustrated on plates xv and xvi of this memoir. 
In the typical species of Dendrograptus, as illustrated under the generic 
description, and in some of the species on plate xvii, we have a wide 
departure from the typical forms of Graptholithus, as developed in the 
characteristic species of the genus (plates i-ix). The strong stem or 
trunk, which is free from cellules, and which has apparently been fixed 
at the base; the irregular branching, which has no bilateral, and apparently 
no definite arrangement, such as observed in all the forms of tree Grap- 
tolithus, are strong points of dissimilarity, and furnish characters for 
generic distinction. The stem and branches are unequally striated longi- 
tudinally, but the form of the celluliferous branches and of the cellules 
offers no important difference (except in the smaller dimensions) from 
those of the stipes or branches of the usual form of graptolites with a 
single series of cellules. In one species referred to this genus (the 
D. gracilis) there is some departure from the typical form of cellules, 
and the body of the stipe is contracted at intervals, while the form of 
cellule and cell-aperture is not unlike some of the Sertularians. 
The genus Callograptus offers forms which are intermediate between 
true Dendrograptus and Dictyonema. In these species, the forms of the 
cellules have not been fully determined. ‘They are marked in one species 
by slight oval pustules, or oval depressions, upon the extremely compressed 
surface of the stipe; but it cannot be satisfactorily shown that this appear- 
ance indicates the normal condition of the cellule or the aperture. If the 
true form be in reality so far different from the usual character of the 
Graptolitidee as these appearances indicate, it may be found necessary to 
separate them from this family. 
The genus Dictyonema is restricted to such forms as have the numerous 
stipes and branches connected by a transverse process, and the whole 
united in a flabelliform or funnel-shaped frond, without elongate stem or 
trunk. The stipes and branches are irregularly striated externally, con- 
sisting of a corneous envelope, as in ordinary graptolites; but I have not 
