Eurypterid is it real & ID

[Trilobit]

I am considering buying this fossil
is it real & what is it?
the seller said it was Balteurypterus tetragonopthalmus
but i cant find anything called that.
any ideas of what it actually is?

[piranha]

The letter 'o' is missing from the seller's listing.

 

'Baltoeurypterus'  is now considered a junior synonym. The Baltic-Ukrainian species is reclassified: Eurypterus tetragonophthalmus

 

 

Fischer de Waldheim, G. 1839

Notice un Crustacé fossile du genre Eurypterus de Podolie.

Bulletin de la Société impériale des naturalistes de Moscou, 11:125-128  LINK

 

Selden, P.A. 1981

Functional morphology of the prosoma of Baltoeurypterus tetragonophthalmus (Fischer)(Chelicerata: Eurypterida). 

Earth and Environmental Science, Transactions of The Royal Society of Edinburgh, 72(1):9-48   PDF LINK

 

Braddy, S.J., & Dunlop, J.A. 1997

The functional morphology of mating in the Silurian eurypterid, Baltoeurypterus tetragonophthalmus (Fischer, 1839).

Zoological Journal of the Linnean Society, 121(4):435-461   PDF LINK

 

Quote:

"Three Silurian representatives of the extinct Eurypterida were scored: Parastylonurus ornatus based on Waterston (1979), Mixopterus kiaeri based on Størmer (1934) and Eurypterus (formerly Baltoeurypterus) tetragonophthalmus based on Selden (1981)."

 

Garwood, R.J., & Dunlop, J. 2014

Three-dimensional reconstruction and the phylogeny of extinct chelicerate orders.

PeerJ, 2:e641 33 pp.   PDF LINK