HYPOGAS´TRIC, _a._ Under or behind the belly. (Little used).
HYPOGNATH´OUS, _a._ Having the under mandible longer than the upper, as
the black skimmer.
HYPOPTI´LUM, _n._ Supplementary plume, or accessory plume, springing
from the same barrel of the main feather. Generally found, but wanting
in many families, and always on the quills of the wings and tail.
Synonymous with _hyporrhachis_ as generally used.
HYPORA´DII, _n. pl._ Barbs of the hypoptilum.
HYPORRHA´CHIS, _n._ Aftershaft; stem or scape of the supplementary
plume. Generally used for the whole of such accessory feather, but best
thus restricted.
HYPOTH´ESIS, _n._ A reasonable presumption or supposition taken as
premise of an argument, or as probably true, to account for what is not
understood. As it does not necessarily rest upon fact, it has not the
weight or dignity of _theory_.
HYPOTHET´ICAL, _a._ Reasonably presumptive: logically supposititious;
conditional; assumed without proof but with fair probability.