On a fossil Crustaceous Animal. 375 



Observations on a fossil Crustaceous Animal of the order 

 Branchiopoda. By J. E. Dekay. Read Dec. 12. 1S25. 



The subject of this notice was presented a few years since, 

 by Professor Noyes of Hamilton College, to the Cabinet 

 of the Lyceum. A label attached to it, purports that it was 

 found in Westmoreland, Oneida County, New-York It has 

 been described in vol. 3. p. 291. of the American Monthly 

 Magazine. The state of the specimen, at that time, not 

 admitting of close examination, Professor Mitchill was in- 

 duced to consider it as a fossil fish, and has described it as 

 belonging to the genus Silurus. This is not surprising, when 

 we recollect for how long a period the naturalists of Europe 

 mistook the fossil salamanders of (Eningen for fishes of the 

 same genus, not to mention the still greater error of consider- 

 ing them as fossil remains of the antediluvial man. 



The following description, with the accompanying plate, 

 will, it is hoped, remove all doubts on the subject, and 

 establish this very singular fossil in its proper place in the 

 system. 



ORDER BRANCHIOPODA. 



Genus Eurypterus. 



Caput a thorace non distinctum. Os ignotum. Oculi 

 duo, sessiles, distantes, lunati. Abdomen elongatum, posticam 

 versus extremitatem sensim gracilius, segmentis transversis 

 subimbricatis divisum. Pedes octo ; duo utrinque antici 

 branchiferi, duo utrinque postici maximi, omnes lamellosi. 

 E. remipes. 



Description. Head roundish, marked anteriorly by a deep 

 indented line formed by the junction of the superior and in- 

 ferior plates, similar to the appearance presented on the 



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