Review of the New York Geological Reports. 309 



Huge beds of tufa are formed where the springs issue between 

 the Hmestone and shale. Springs issuing from this formation 

 are occasionally charged with sulphuretted hydrogen. 



The Niagara group is every where highly fossiliferous, particu- 

 larly the shale. Shells, trilobites, and crinoidea, are most abun- 

 dant in the shale; and corals in the limestone. Already six spe- 

 cies of trilobites, nine species of crinoidea, and about as many 

 mollusca, have been recognized as belonging exclusively to the 

 shale. The corals are for the most part much decomposed, 

 which makes it difficult to distinguish the species. 



The following are some of the most common trilobites of the 



shale. 



1. 2. 



y'^^ 



Fig. 1. Asaphus limulurus. 2. Head of Asaphus limulurus. 

 3, Calymene Niagarensis. 4. Bumastis Barriensis. 



Vol. xLTiii, No. 2.— Jan.-March, 1845. 40 



