50 CANADIAN FOSSILS. 
I refer these fossils, with hesitation, to the genus Oldhamia ( O. fruticosa, 
Hall). 
The variety of form and mode of development among the graptolites 
is shown, by these collections from the Quebec group, to be much greater 
than had ever before been supposed. ‘The number of species which have 
been traced to their origin, and whose mode of growth has been verified, 
is probably larger than in all the collections heretofore made ; and, together 
with those before known, enables us to give a very full exposition of the 
characters of this family of fossils. 
SYNOPSIS OF THE GENERA OF GRAPTOLITIDA. 
Te 
Species consisting of stipes or fronds, with a bilateral arrangement of the parts ; 
a solid axis, with a common canal extending along each series of cellules, 
1. The successive buds developed in tubular cellules, 
which are usually in contact for a greater or less pro- 
portion of their length, and inclined towards the axis. 
a. Cellules in single series along one side of a com- 
mon solid axis. Stipes, two or more, from a com- 
mon’ origin, with or without a central disc. Sub- 
genera Monoprion,* Didymograptus, Monograptus, 
Tetragraptus, ete. 
. Cellules on one side of slender branches, which 
are developed on one or two sides of a long slender 
axis or rachis, the free. extremities of which are 
likewise celluliferous. Hx. G. gracilis and G. diver- 
gens. | 
c. Cellules developed in aie arrangement on two | 
ao 
GRAPTOLITHUS, Linneus. 
sides of a common solid axis. Stipes narrow elon- 
gate. Sub-genus Diprion, = Diplograptus. 
d. Cellules developed in a cruciform arrangement on 
the four sides of a common or coalescent axis. 
Stipes elliptical or sub-elliptical. 
Puytiograptus, Hall, 
2. Cell-apertures excavated in the margins of the stipes, 
without tubular or cup-form extension; the cell- 
apertures upon one or both sides of the stipe. 
Graptolithus bicornis and others. 
Cumacograptus, Hall. 
3. Solid axis eccentric or sub-exterior, with cellules de- 
veloped in parallel ranges on opposite sides of the 
stipe, and in contact throughout their entire length. 
a. Known only as separate stipes, with reticulate 
test. 
b. Occurring as simple stipes, and as compound 
fronds; test smooth. 
} Retiotites, Barrande. 
} Retiogrartvus, Hall. 
* Should it be proved that there exist simple stipes with a single range of cellules, 
the definition of this section will require to be modified, or a new sub-section made to 
include such forms. 
