1865.] GRAPTOLITES OF THE QUEBEC GROUP. 51 



the true graptolites, as well as of their congeners of the same family. 

 Notwithstanding the presence of the radicle or initial point obser- 

 vable in so many species, it does not afford evidence of attachment 

 to the sea-bottom or to some other substance, at least in the mature 

 condition. In all the monoprionidian forms, however much or 

 little extended the radicle may be, it is always smooth, and taper- 

 ing to a point. In many of these, and more especially in those 

 with a central disc, this radicle is reduced to a minute protuber- 

 ance, and is often scarcely or not at all perceptible. 



The same is essentially true of the greater number of diprioni- 

 dian forms examined. In these the solid axis is sometimes 

 extended beyond the base of the stipe, and terminated as if broken 

 off abruptly; while there is often a slender oblique process on each 

 side of the base. 



In Retiograptus and Phyllograptus there is not the same evi- 

 dence of completeness at the base of the radicle. The lower ter- 

 mination, when it can be fully examined, is broken, as if there 

 had been a further continuation of this part, though it exhibits no 

 enlargement. I have inferred that all these, like the example of 

 Retiograptus eucharis, have constituted parts of a similar com- 

 pound body, and are but the separated stipes of the frond. If 

 this be true, their mode of existence is not unlike the other 

 species with compound fronds and a central disc. 



In G. bicornis the extension of the solid axis below the base of 

 the stipe is not always preserved ; but when it is entire, we find 

 two strong diverging and slightly-curving processes or spines from 

 the base, having smooth terminations. Sometimes a disc or bulb, 

 of the same substance as the stipe, extends between these spines, 

 and in the compressed condition envelops a few of the lower 

 cellules. 



The expansion at the base of this species has the same general 

 appearance as the central disc of G. Logani, G. Headi, and others ; 

 showing that this sort of development of the substance is not alone 

 characteristic of those forms having several stipes united at the 

 base. In other examples this basal expansion is contracted in 

 such a manner as to give a crescent-form to the lower extremity ; 

 but in all these gradations, the margins of this part are entire and 

 unbroken. 



We have seen that the youngest forms of the diprionidian grap- 

 tolites, those which we may suppose had but recently escaped 

 from the reproductive sac, are furnished with the minute radicle- 



