The Collaborative International Dictionary of English v.0.48:

Neocomian \Ne`o*co"mi*an\, n. [From Neocomium, the Latin name of
   Neuchatel, in Switzerland, where these rocks occur.] (Geol.)
   A term applied to the lowest deposits of the Cretaceous or
   chalk formation of Europe, being the lower greensand.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Neocomian \Ne`o*co"mi*an\, a. (Geol.)
   Of or pertaining to the lower greensand.
   [1913 Webster]