After "Triceratops" was described, between 1889 and 1891 Hatcher with great effort collected another thirty-one of its skulls. The first species had been named "Triceratops horridus" by Marsh. Its specific name was derived from the Latin "horridus"; "rough, rugose", perhaps suggesting the roughened texture of those bones belonging to the type specimen, later identified as an aged individual. The additional skulls varied to a lesser or greater degree from the original "Triceratops" specimen. This variation is unsurprising, given that "Triceratops" skulls are large three-dimensional objects, coming from individuals of different ages and both sexes, and which were subjected to different amounts and directions of pressure during fossilization.