DEVONIAN ROCKS OF CANADA WEST. 108 



8th. The pores are usually distant half a line from each otherj but 

 sometimes either less or more than that distance. 



9th. The longitudinal lines on the faces of the tube may be either 

 present or absent, in different parts of the same specimen, and it is in 

 general much more strongly developed in the Devonian than in the 

 Silurian rocks. I have seen it on European specimens. 



If the observer, while examining any large collection of specimens 

 from the upper Silurian or Devonian rocks of Canada, keep in mind 

 and direct his attention to the investigation of the above characters, he 

 will find innumerable shades of difference which will soon convince 

 him that if they are to be regarded as of specific value, it would require 

 nearly fifty specific definitions to give them all expression. It is 

 scarcely necessary to state that a division to one-fourth of that extent 

 would be absurd, and injurious to science. The species which I be- 

 lieve to have been too unguardedly set apart from F. Gothlandica are 

 JP. Goldfussi, F. Troosti, M Niagarensis, Astrocerium parasiticum, 

 and A. pyriforme. 



The first of these, JP. Goldfussi, (Edwards and Haime), was sup- 

 posed to be different from F. Gothlandica, because although there 

 were in general two rows of pores, yet some of the sides of the tubes 

 exhibit one, and others three rows, and further that the pores are 

 nearer together than in the typical species. I am perfectly satisfied 

 that neither of these characters are sufficient. 



F. Troosti, (Edwards and Haime.) Founded on the presence of 

 the longitudinal lines on the faces of the tubes, is also not distinct, as 

 that character occurs throughout the series. 



F. Niagarensis, (Hall,) is thus described : — " Spheroidal or irregu- 

 lar in form, rapidly increasing by interstitial cells ; walls of cells usually 

 thin, pierced by two rows of minute pores ; transverse septa thin, often 

 oblique, or bent downwards." Professor Hall further states that it 

 " differs from the F. Gothlandica in forming more usually small sphe- 

 roidal masses, and in the rapid increase of cells almost entirely by 

 interstitial growths, the base continuing small. The size of the cells 

 is always less than in that species, and from this character alone it 

 may be distinguished." 



I think that this species consists of young pyriform or spheroidical 

 colonies of F. Gothlandica or F. basaltica, and also that the other 

 two A. parasiticum and A. pyriforme are the same. Wherever F. 

 Gothlandica and F, basaltica occur, these small specimens are more 

 or less common. 



