556 



HISTORICAL GEOLOGY. 



A dike of a chrysolitic eruptive rock, altered to serpentine, intersects the Salina 

 group at Syracuse (though now concealed from view), which was first described by 

 Vanuxem in 1839, and by Beck in 1842, and has recently been studied and explained by 

 G. H. Williams {Am. Jour. Sc, 1887). 



794-797. 



LIFE. 



The fossils that have been supposed to occur in the lower beds of the 

 Salina group in ISTew York are referred to the Niagara group, and those at 

 the top are Water-lime species. Regarding the Water-lime beds of Ohio as 

 sjoichronous with the Salina and Water-lime of New York, the fossils of 

 the Water-lime stand for those of the Onondaga period. But they are few 

 in number, the limestone having originated, as its fine texture and impurity 



show, in shallow waters, under their gentle 

 triturating action, and differing in origin from 

 the Salina beds in having had more open 

 connection with the Interior Continental Sea. 

 Unquestioned remains of Fishes are among 

 the fossils, and also the first of American 

 terrestrial species, a Scorpion. 



Some of the characteristic fossils of the 

 Water-lime are represented in the annexed 

 figures. Fig. 794 is the more common species 

 of Tentaculites of the Tentaculite limestone, 

 and 795 is the same enlarged. It is regarded 

 as the shell of a small Pteropod. Fig. 796 

 is an Ostracoid Crustacean (^Leperditia alta); 

 it is very common in the 

 Tentaculite limestone and 

 Water-lime. Fig. 797 represents a young Eurypterid 

 [Euryptertis remipes), a common species in the Water- 

 lime, related to the species of the Trenton period, 

 mentioned on page 513, but of different genus. Some 

 specimens are a foot in length. E. giganteus, a species 

 from near Buffalo, described by J. Pohlman, was nearly 

 six inches broad and probably 20 inches long. The under 

 surface of E. remipes restored is shown in Fig. 798 ; and 

 on it the segments of the thorax and abdomen are num- 

 bered. Anteriorly, the members of the cephalic portion 

 are five in number of pairs, and they serve both as feet 

 and jaws, as in the modern Limulus. There are no anten- 

 nae corresponding to the chelate or pincer-like antennae Restoration of Euryptems 

 of Limulus. Behind the legs, an apron-like pair of m, mouth. Haii. 

 limbs, with a narrow prolongation at the center, per- 

 tains to the first thoracic segment, which has the position of a similar pair 

 in Limulus. 



Figs. 794, 795, Tentaculites gyracantlius ; 

 796, Leperditia alta ; 797, Eurypterus 

 remipes, the three anterior legs of the 

 right side mutilated, a young individ- 

 ual. Meek. 



