556 trans. st. louis acad. scie.vce. 



Occurrence of Graptolites. 



The Graptolites are almost entirely derived from the quarries at 

 or near the "Jolly-cut road," south of Hamilton. As few fossils 

 of the Niagara group in Ontario can be said to be abundant, so the 

 Graptolites are scarce ; yet it will be seen that the varieties are 

 numerous. The beds in which they are principally found are 

 those about six feet above the base of the " chert beds," and in 

 the more shaly dolomites immediately underlying. In these last 

 rocks the specimens are in a better state of preservation, espe- 

 cially at their earthy partings, though easily obliterated. 



The only fossils of this family, that I have seen in the Clinton 

 beds, are obscure or poorly preserved specimens of the genus 

 Dictyonema. 



In the following descriptions I have often been compelled to 

 depend almost entirely upon the size of the stipes and the mode 

 of branching, as the cellular structure has been obliterated in the 

 majority of cases, even when the general form of the frond is per- 

 fectly distinct. This arises from the fact that the greatest varie- 

 ties of species occur in the cherty dolomites, where, although the 

 carbonaceous matter remains, the semi-crystallization of the dolo- 

 mitic earth has obliterated the internal structure. 



It sometimes happens that where the carbonaceous matter is 

 removed the impressions of the cellular orifices are retained 

 on the surfaces of the stone. Again, where extremities of the 

 branches are broken oft" and the cellular arrangements are ob- 

 scure, it is impossible to do anything with the fragments ; and 

 no doubt there are many undescribed species yet remaining in 

 the group o( fossils at Hamilton. 



The material from which I worked out more than thirty 

 species consisted of between three and four hundred specimens 

 belonging to my own collection, and supplemented by those of 

 McGill University and the Canadian Geological Survey. The 

 amount of work in classifying them was very great, as there is a 

 considerable variation in the forms, producing an inclination to 

 make too many species. As much time, as my professional du- 

 ties would permit, has been devoted to the subject, yet the work 

 must be regarded as incomplete. In 1878 a notice of a few spe- 

 cies of Graptolites was published in the Canadian Naturalist for 

 that year. Even of the species there described much better ma- 

 terial has since been obtained, and a revision is here included. 



