284 



ARACHNIDA EURYPTERIDA 



The Eurypterid which is best known is Eurypterus fischeri 

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

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



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Fig. 161. — Eiirypterus fischeri, Eichw. Upper SUurian, RootzikiUl, Oesel. Dorsal 

 surface, a. Ocellus; b, lateral eye; 2-6, appendages ofprosoma; 7-12, segments 

 of mesosoma ; 13-18, segments of metasoma ; 19, taal-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. Edinb. xxx., 1882, p. 511; Laurie, ibid, xxxvii., 1892, 

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



