SALINA PERIOD. 



249 



II. Life. 



The Salina beds are for the most part destitute of fossils. The 

 lower beds in New York contain a few species imperfectly pre- 

 served ; and the same is true of the upper. The latter, however, 

 are regarded as rather of the next (Upper Helderberg) period. 



In the limestone at Gait there are a number of shells, and two of them — Mur- 

 chisonia Boydii and Cydonema sulcata — are set down by Hall as identical with 

 species in the lower part of the Onondaga Salt group. The fossils of this and 



Fi£. 416 A. 



Megalonms Canadensis. 



the Leclaire limestones have been shown by Hall to be very different from those 

 of the Niagara beds. 



Fig. 416 A represents one of the Conchifers, the Ifegalomus Canadensis, a 

 species that is occasionally found four inches long. Besides this there are a 

 Pentamerus, P. occidentalis, a species of Murchisonia, an Orthoceras, and a 

 Calymene. 



General Observations. 



Geography. — The position of the Saliferous beds over the State 

 of New York indicates that the region which in the preceding 

 period was covered with the sea and alive with Corals, Crinoids, 

 Mollusks, and Trilobites, making the Niagara limestone, had now 

 become an inferior shallow basin, or a series of basins, mostly shut 

 off from the ocean, where the salt waters of the sea, which were 

 spread over the area at intervals, — intervals of days or months, it 

 may be, — evaporated and deposited their salt over the clayey bot- 

 toms. In such inland basins the earthy accumulations in progress 



