\Pyc`no*gon"i*da\, n. pl. [NL., fr. Gr. ? thick
crowded + ? knee.] (Zo["o]l.)
A class of marine arthropods in which the body is small and
thin, and the eight legs usually very long; -- called also
{Pantopoda}.
Note: The abdomen is rudimentary, and the triangular mouth is
      at the end of a tubular proboscis. Many of them live at
      great depths in the sea, and the largest of them
      measure two feet across the extended legs.