( n. )
Any one of numerous species of fossil brachipods of the genus Spirifer, or Delthyris, and allied genera, in which the long calcareous supports of the arms form a large spiral, or helix, on each side.
( n. )
Any one of numerous species of fossil brachipods of the genus Spirifer, or Delthyris, and allied genera, in which the long calcareous supports of the arms form a large spiral, or helix, on each side.
Webster's Revised Unabridged English Dictionary. Пересмотренный полный словарь английского языка Webster. 2012