Webster's Revised Unabridged Dictionary · 1913

Pycnogonida

Pycnogonida , noun, plural

[New Latin, from Greek {not transcribed} thick crowded + {not transcribed} knee.]

(Zoology) 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.