284 



ARACHNIDA EURYPTERIDA 



CHAP. 



The Eurypterid which is best known is Eurypterus fischeri 

 (Figs. 161, 162), which is found in the Upper Silurian rocks tit 

 Eootziklill in the Island of Oesel (Gulf of Eiga). In the 



FIG. 161. Eurypterus fischeri, Eichw. Upper Silurian, Rootziktill, Oesel. Dorsal 

 surface, a, Ocellus ; b, lateral eye ; 2-6, appendages of prosoma ; 7-12, segments 

 of mesosoma ; 13-18, segments of nietasoma ; 19, tail-spine. (After Holm.) 



Eurypterids from other deposits the chitinous exoskeleton has 

 been altered into a carbonaceous substance, but in the specimens 

 from Oesel the chitin is perfectly preserved in its original 



1866-78, and Geol. Mag. 1879, p. 196 ; 1887, p. 481 ; 1888, p. 419 ; 1907, p. 277 ; 

 Peach, Trans. Roy. Soc. Edirib. xxx., 1882, p. 511 ; Laurie, ibid, xxxvii., 1892, 

 p. 151 ; xxxvii., 1893, p. 509 ; and xxxix., 1899, p. 575. 



