NIAGARA GKOUP. 173 



solid space where no cells appear ; and it often happens that some other species of coral has 

 commenced growth upon this species, as in the example figured. 



Fig. 6 a. A fragment of an Orthoceras covered by this coral, showing at two points a', a", the 



growth of other corals upon this one. 

 Fig. 6 b. An enlarged portion of the surface, showing the form and arrangement of the cells in 



this species, and in a species of Callopora which covers it in parts. 



Position and locality. This coral occurs attached to Orthocerata in the shale at Rochester, 

 Marshall's mill, and Lockport. 



PLATE XL E. Fig. 7 a, h. 



An incrusting coral enveloping a Stephanocrinus. The form of the shallow cells is different 

 from any mature species yet observed in this rock ; and probably it is only the commencement 

 of growth of a coral or bryozoa, which, in a perfect or mature condition, presents a ditferent 

 character. Should it prove to be a mature form, it will find its analogues in the Flustra or 

 Eschara type. 



Fig. 7 a. The coral enveloping a broken crinoid. 

 Fig. 7 b. An enlargement of a portion of the surface. 



Position and locality. In the shale at Lockport 



PLATE XL E. Fig. 8 a, b. 



An incrusting^ membrano-calcareous coral, growing upon Lichenalia and other bodies. 

 Coral composed of tubular cells, which increase by regular dichotomizing, transversely striate 

 or rugose ; a nearly circular apeilure of each simple tube, opening upward, at the point where 

 bifurcation takes place. 



This species is very peculiar and charactei'istic, probably forming the type of a distinct genus. 

 Its mode of growth is somewhat like Aulopoea, but the tubes are more minute, closely ad- 

 hering to the body to which it is attached, and placed laterally in juxtaposition. The frequent 

 bifurcation of these tubes causes a rapid expansion of the coral, and it spreads in nearly circular 

 or flabellate blotches. 



Fig. 8 a. A portion of Lichenalia, on which this coral is growing. 



Fig. 8 b. An enlargement showing mode of growth and character of tubes. 



Position and locality. In the shale at Lockport, growing upon Lichenalia and other corals. 



