284 



ARACHNIDA EURYPTERIDA 



The Eurypterid which is best known is Euryptcrus Jischeri 

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

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



Fig. 161. — Eurt/pterus Jischeri, Eichw. Upper Silurian, Rootzikiill, Oesel. Dorsal 

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

 of niesosoma ; 13-18, segments of metasoma ; 19, ta41-spine. (After Holm. ) 



Eur^'pterids 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 Gcol. Mag. 1879, p. 196 ; 1887, p. 481 ; 1888, p. 419 ; 1907, p. 277 ; 

 Peach, Trans. Hoy. Soc. Edinb. xxx., 1882, p. 511 ; Laurie, ibid, xxxvii., 1892, 

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



