The Collaborative International Dictionary
Pygidia
Pygidium \Py*gid"i*um\, n.; pl. Pygidia. [NL., fr. Gr. ?, dim. of ? the rump.] (Zo["o]l.) The caudal plate of trilobites, crustacean, and certain insects. See Illust. of Limulus and Trilobite.
Wiktionary
pygidia
n. (plural of pygidium English)
WordNet
pygidia
See pygidium