CHAPTER XI 



ARACHNIDA (CONTINUED) DELOBEANCHIATA = MEROSTOMATA 



(CONTINUED) EURYPTERIDA 



Order II. Eurypterida. 



THE Eurypterida or Gigantostraea are found only in the 

 Palaeozoic formations. Some species of Pt&rygotus, Slimonia, 

 and Stylonurus have a length of from five to six feet, and are 

 not only the largest Invertebrates which have been found fossil 

 but do not seem to be surpassed in size at the present day except 

 by some of the Dibranchiate Cephalopods. All the Eurypterids 

 were ;i qua tic, and, with the possible exception of forms found in 

 the Coal Measures, all were marine. The earliest examples 

 occur in the Cambrian deposits, and the latest in the Permian ; 

 but although the Eurypterids have thus a considerable geological 

 range, yet it is mainly in the Silurian and the Old Ked Sand- 

 stone that they are found, the principal genera represented in 

 those deposits being Enrypterus, Stylonurus, Slimonia, Pterygotus, 

 Hur/hmilleria, Dolichopterus, and Eusarcus. From the Cumbrian 

 rocks the only form recorded is Strabops;^ in the Ordoviei.m 

 the imperfectly known Echinognathus' 1 and some indeterminable 

 fragments have alone been found. In the Carboniferous deposits 

 Enrij}>t<'riis and Glyptoscorpius occur, and the former survived 

 into the Permian. 3 



1 Walcott has described, under the generic name /:,//iin/, ini]iert< linens 



from the Al^'nikian (i>re-Camhrian) of .Mmit.ina, \\hieh he thinks m;iy lie the 

 remains of Kurypterid.s (Bull. Gent. ,S'm-. America, x., ISDi), \>. 



- Walcott, A-mi'i: Jiir. ,SV/. (:j), xxiii., 1882, p. L']::. 



3 Descriiitions and figures of I'.ritisli Knryptcrids are ^ivrii in the following 

 works : Huxley and Salter, " Pterygot us," M,-,n. Geol. Survey, /:>;/. Org. /' 

 mains, i., 18;iO ; H. Woudwanl. " .Mnn.>^ra|ili (if the M.^n^toinata," r.ilmnnl. 



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