Virions not occluded, or occluded by protein bodies or crystals in thin sections (sometimes); not enveloped. Virions one type of particle only.
Capsids isometric. Capsid shell of virion composed of two layers, or three layers; shell of virion all usually present, or outer often lost. Nucleocapsids with obvious regular surface structure; 60-80 nm in diameter. Symmetry icosahedral. Nucleocapsids appear to be round. Surface capsomer arrangement obvious. Surface projections of nucleocapsid not seen (surface apparently smooth), or not present, or distinct; spikes; restricted to (the 12 vertices). Incomplete virus particles often present; are empty capsids, or are incompletely assembled capsids. Virions only of
icosahedral