The Collaborative International Dictionary of English v.0.48:

Descendent \De*scend"ent\, a. [L. descendens, -entis, p. pr. of
   descendre. Cf. Descendant.]
   Descending; falling; proceeding from an ancestor or source.
   [1913 Webster]

         More than mortal grace
         Speaks thee descendent of ethereal race. --Pope.
   [1913 Webster]

WordNet (r) 3.0 (2006):

descendent
    adj 1: going or coming down [syn: descendant, descendent]
    2: proceeding by descent from an ancestor; "descendent gene"
       [syn: descendant, descendent]
    n 1: a person considered as descended from some ancestor or race
         [syn: descendant, descendent] [ant: ancestor,
         antecedent, ascendant, ascendent, root]