submarginal
adjective
- below minimum requirements or standards: submarginal housing
- not yielding a satisfactory return; not profitable: submarginal land
- Biol. near the margin of an organ or part
See submarginal in American Heritage Dictionary 4
sub·mar·gin·al
adjective- Near the margin of a body, organ, or part: submarginal tentacles.
- Of low productivity; infertile.