14 CANADIAN FOSSILS. 
Fig. 17. Fig. 18. 
$e we 
GRAPTOLITHUS GRACILIS.* 
We have still another group, presenting some differences, more particu- 
larly in the development and form of cellules, than in their general form ; 
and seeming in some species to unite the characters of those having a 
single range, with those having a double range of cellules. The simpler 
forms of this type are similar to the two-stiped forms of the first series ; 
but in all those, whether of two, four, or more stipes, the cellules are 
developed on the upper side, or that side opposite to the initial point. In 
species like G. sextans, G. divaricatus, and others of this type, the 
cellules are on the lower, or same side with the radicle. 
Fig. 19. 
GRAPTOLITHUS DIVARICATUS: 
and enlargement of cellules. 
In the accompanying figure of G. divaricatus, the frond consists of two 
simple uniserrate stipes ; and the same is true of Gf. sextans, except that 
* The fig. 18 was theoretically constructed, but has since been verified by the discovery 
of a specimen having the same form and arrangement of parts. 
