V 



BIKDSEYE LIMESTONE. 37 



BIRDSEYE LIMESTONE. 



FOSSIL PLANTS? OF THE BIRDSEYE LIMESTONE. 

 Plates VIH. & IX. 



The Birdseye limestone is well developed along the valley of the Mohawk river ; and 

 in many places, owing to the absence of the Chazy limestone just mentioned, it succeeds 

 directly to the Calciferous sandstone. It is distinguished by its thick layers, evenly bedded 

 structure, and well marked vertical joints, which give the rock, when quarried, the ap- 

 pearance of a wall. It is usually of a bluish grey or light dove color, weathering to a light 

 ashen grey : in its western extension it loses its bluish shade, becoming lighter in color. 

 The rock is fine-grained or compact, breaking with a conchoidal fracture, the surface 

 presenting numerous crystalline points or spots. 



The organic remains of this rock are not numerous in species ; but their existence, though 

 often very obscure, has given it a lithological character, by which it is known over a wide 

 extent of country, and from which its name has been derived. The peculiar forms described 

 in the succeeding pages ( Plates VIII. & IX.) enter largely into the rock, and in many 

 places constitute no small portion of the whole mass. They are frequently partially 

 obliterated by crystallization ; but in far the greater number of instances, a weathered 

 surface exhibits them in greater or less perfection ; and although the species are so few, 

 there is no rock better characterized than this one by its palaeozoic features. The form and 

 mode of growth are such as to distinguish these fossils from all preceding or succeeding 

 forms ; and though «t single stem may resemble other marine vegetation, yet, when taken 

 in combination, they present features totally distinct and unique. In the most prominent 

 species, the stems are vertical to the strata ; and they are, as it were, tied together at 

 intervals throughout their whole extent, by diverging branches which unite with the 

 contiguous stems on all sides. In this respect, they present a feature unknown in either 

 the corals or marine plants of the Fucus family. Their internal structure also presents some 

 similar anomalies ; for while we find in some parts a structure like the cellular tissue of 

 ordinary plants, we find, in others, cells or tubes bearing some analogy to the zoophytes. 

 The substance also appears to have been partially calcareous or corticiferous, at least the 

 external coat. In order, therefore, to give some expression to this apparent combination of 

 structure, if such it prove to be, I have proposed a distinct generic name, to include at least 

 two well-marked species. 



