The Collaborative International Dictionary of English v.0.48:

Shagbark \Shag"bark`\, n. (Bot.)
   A rough-barked species of hickory (Carya alba), its nut.
   Called also shellbark. See Hickory.
   (b) The West Indian Pithecolobium micradenium, a legiminous
       tree with a red coiled-up pod.
       [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Shellbark \Shell"bark`\, n. (Bot.)
   A species of hickory (Carya alba) whose outer bark is loose
   and peeling; a shagbark; also, its nut.
   [1913 Webster]

WordNet (r) 3.0 (2006):

shellbark
    n 1: North American hickory having loose grey shaggy bark and
         edible nuts [syn: shagbark, shagbark hickory,
         shellbark, shellbark hickory, Carya ovata]