slimonia

from The Century Dictionary.

• noun A genus of extinct merostomatous crustaceans of the family Eurypteridæ, of large size, with subquadrate cephalothorax, the preoral appendages small and chelicerate, five pairs of postoral appendages of which the first is antenniform, the first six of the twelve abdominal segments represented on the ventral side by parts of the genital plate, and four discontinuous plates bearing branchial lamellæ. The genus is found in the Old Red Sandstone of Scotland.