The Collaborative International Dictionary of English v.0.48:

Camarasaurus \Cam`a*ra*sau"rus\, n. [NL. fr. Gr. ? a vaulted
   chamber + ? lizard.] (Paleon.)
   A genus of gigantic American Jurassic dinosaurs, having large
   cavities in the bodies of the dorsal vertebr[ae].
   [1913 Webster]