558 TRANS. ST, I-OUIS ACAD. SCIENCE. 



polyps. In the same year McCoy described the first form with 

 a double row of cells. In 1852, Geinitz changed his view and 

 placed them amongst Zoophytes, and proposed several new ge- 

 neric names. Since that date many new species have been added 

 to the list, mostly by the geologists above referred to. The two 

 greatest additions to our knowledge of this fauna in America 

 have been made by Prof. Hall in the descriptions of a large num- 

 ber of species from the Utica and Hudson Groups, and still more 

 recently from the Quebec Group of Canada. (See Prof. Hall's 

 20th Report N. Y. State Museum of N. N.) 



Geological Distribution. 



Fiom Prof. Hall's list of Graptolitcs we find one species in the 

 Potsdam ; fifty-three species (belonging to twelve genera) in the 

 Qiiebec Group (Upper Cambrian) ; four species in the Trenton ; 

 thirty species, of eight genera, in the Utica and Hudson River 

 Group (Cambro-Silurian) ; two species in the Clinton ; three 

 species in the Niagara ; one species in the Corniferous, and two 

 species in the Hamilton formations. To this list there have 

 subsequently been added two species, and four of Dawsonia 

 (supposed to be graptolitic ovarian sacs) in the Qiiebec group ; 

 one in the Trenton, and six in the Niagara formation. 



In 1878, in a paper in Canadian Naturalist, I added three new 

 genera and nine additional species as occurring in the Niagara 

 formation at Hamilton, Ontario. In the present paper, inc ud- 

 ing those formerly describetl by myself, I add to the list of 

 American Graptolites four additional genera and thirty new spe- 

 cies, making in all forty-one known species of twelve genera 

 belonging to the Upper Silurian formations. 



From this analysis of the geological distribution, we easily see 

 the great antiquity of this type of organisms, and the very im- 

 portant addition that has been discovered, not only of the variety 

 of forms, but also in a horizon so high. 



Of those formerly known, with the exception of the few species 

 in Trenton limestone and a few more in somewhat harder Hud- 

 son River calcareous shales, almost the whole fauna is confined 

 to shaly beds. Those obtained at Hamilton, in the Niagara for- 

 mation, are mostly in dolomitic limestones, or at most in only 

 slightly shaly limestones. 



