(noun; French plastron
, breast plate): 1. The chorion
of some eggs.
2. (Arthropoda: Insecta) A permanent film of air retained by hairs on the outside of an aquatic insect body allowing an air water interface for gaseous exchange.
3. Echinodermata: Echinoidea) In Spatangoida, a ventral interambulacral area between the labrum and periproct, sometimes with special spination.