The Collaborative International Dictionary of English v.0.48:

Corneous \Cor"ne*ous\ (-?s), a. [L. corneus, fr. cornu horn.]
   Of a texture resembling horn; horny; hard. -- Sir T. Browne.
   [1913 Webster]

WordNet (r) 3.0 (2006):

corneous
    adj 1: made of horn (or of a substance resembling horn) [syn:
           corneous, hornlike, horny]

Moby Thesaurus II by Grady Ward, 1.0:

34 Moby Thesaurus words for "corneous":
   bony, cement, cemental, concrete, dense, diamondlike, dure,
   flintlike, flinty, granitelike, granitic, hard, hard as nails,
   hardhearted, horny, iron-hard, ironlike, lapideous, lithoid,
   lithoidal, marble, marblelike, obdurate, osseous, resistant,
   resistive, rocklike, rocky, solid, steellike, steely, stonelike,
   stony, tough