12 CANADIAN FOSSILS. 
a form of cellule similar to that in observed fragments of the ordinary 
species of graptolites. The cellules are very minute, and, from the 
frequent ramifications, this would probably always be recognized as a 
branching species. 
Some of the forms of Dendrograptus have slender spreading branches, 
and less rigid stems than the typical species, but still retain the angular 
cellules, as in figs. 1 and 2 of plate xvii. From these we pass almost 
imperceptibly to the slender spreading forms which I have termed Callo- 
graptus, plate xix, in which there is, apparently, some slight modification 
in the form of the cellule ; and on the other hand, there is an almost insen- 
sible gradation to the Dictyonema, plate xx, in which the branches are 
connected by lateral bars, and the whole developed in a flabelliform or 
funnel-shaped. frond, with angular cellules on the inner margins of the 
branches. (Fig, 10, plate A.) 
DICTYONEMA RETIFORMIS. 
There are certain forms of graptolites, which, though possessing linear 
straight or slightly curving stipes and angular cellules, like the typical 
species, have yet a different aspect, and do not so naturally fall into the 
series. Among these we find Graptolithus divergens (fig. 11), where the 
bilateral relation of the parts is still shown, but the celluliferous stipes or 
branches are arranged on the two sides of a slender stipe or rachis, and 
diverge on each side from what appears to be the centre or initial point. 
Different specimens show some slight variations of these characters, but 
not any essential differences. 
