Pyc`no*gon"i*da (?), n. pl. [NL., fr. Gr. thick crowded + knee.] Zool.
A class of marine arthropods in which the body is small and thin, and the eight legs usually very long; -- called also Pantopoda.
⇒ 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.
© Webster 1913.