Hughmilleria socialis
Late Silurian
Salina Group, Vernon Formation, Pittsford Member
Pittsford, New York, USA
133mm near-complete rare eurypterid on 153mm slab. Only the second one of these we have ever had. Matrix in the upper right corner is restored, fossil itself has no repair or restoration at all.

Illustrated in the famous book “The Eurypterida of New York” (digital copy available here), this species is considered the most primitive known pterygotid eurypterid. Notice the more streamlined head than the more well known Eurpypterus and how the eyes are off to the sides of the body.