The ventral nerve cord of the spiny lobster, Panulirus argus was examined by transmission and scanning electron microscopy. Tannic acid mordant stain was used to enhance extracellular filaments. The ventral nerve cord is surrounded by an unusual perineurial sheath composed primarily of interwoven extracellular filaments. Gap junctions were found associated with the glial cells making up the perineurium. The axo-glial wrappings also contained extracellular filaments associated in bundles rather than uniformly around the axons. The extracellular filaments of the perineurium and axo-glial wrappings appeared to be morphologically identical with diameters ranging from 10-15 nm.