Source : Webster's Revised Unabridged Dictionary (1913)

Agnation \Ag*na"tion\, n. [L. agnatio: cf. F. agnation.]
   1. (Civil Law) Consanguinity by a line of males only, as
      distinguished from cognation. --Bouvier.

Source : WordNet®

agnation
     n : line of descent traced through the paternal side of the
         family [syn: {patrilineage}]