NrAGARA OROtTP. 



125 



515. 1. FAVOSITES NIAGARENSIS. 



PL. XXXIV A. Fig.io-h. 



Spheroidal or irregular 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 down- 

 wards. 



The first specimens in which I have detected pores in the walls of the cells, and at the 

 same time the entire absence of rays, were from the limestone at the top of Niagara Falls, or 

 even a few- feet higher, being at the southeastern side of Goat island. In these specimens the 

 walls of the cells are very thin, and likewise the septa, which are frequently bent or oblique 

 to the axis of the tube. The pores are often very distinctly visible in the sides of the cells. In 

 a spherical specimen from near Rochester, the walls of the cells appear stronger and thicker ; 

 but this is probably due to their being replaced with silex, and thus thickened. The pores are 

 likewise larger than in the specimens from Niagara Falls. 



I have included with this species, one from Milwaukie, in which I am unable to distinguish 

 any specific difference. 



Fig. 4 a. A fragment from the limestone at Goat island, showing the ends of the cells which are 

 open. 



Fig. 4 5. A portion enlarged, showing the transverse septa and pores in the walls of the cells. 



Fig. 4 c. A small spherical form, having the cells open, and the walls replaced by siliceous matter. 



Fig. i d. A small portion enlarged, looking into the cells and showing the perforated walls. 



Fig. 4 e. A worn specimen from the lower part of the limestone at Lockport. The cells are open, 

 but there are no pores visible. 



Fig. 4 /. A section of a small mass of apparently the same species, showing the septa bent 

 downwards. 



Fig. i g. A longitudinal section of another specimen, in which the septa appear at irregular in- 

 tervals, some of them at great distances, probably from a part of the original number 

 having been obliterated ; and others in close proximity, showing that this feature can 

 not be relied upon to characterize specific distinctions. 



Fio-. 4 h. Transverse section, showing the ends of the cells and the separation of the walls^ 

 forming distinct and separate tubes. , 



The three last figures are taken from specimens in which a partial or entire substitution of 

 the original has taken place by a kind of semicrystalline calcareous matter, which has appa- 

 rently obscured or filled up the pores in the sides of the cells, as none are visible. 



This species differs from the F. gothlandica., in forming more usually small spheroidal masses, 

 and in the rapid increase of cells almost entirely by interstitial .growth, 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. 



