The fourth eurypterid genus to be described (following "Hibbertopterus" in 1836 and "Campylocephalus" in 1838, not identified as eurypterids until later), out of those still seen as taxonomically valid in modern times, was "Pterygotus", described by Louis Agassiz in 1839. "Pterygotus" was considerably larger in size than "Eurypterus" and when the first fossils were discovered by quarrymen in Scotland they were referred to as "Seraphims" by the workers. Agassiz first thought the fossils represented remains of fish, with the name "Pterygotus" meaning "winged fish", and only recognized their nature as arthropod remains five years later in 1844.