Honeycomb Crust
Many hextherma drifted into the vents within the mid-Vailnoff Ridge. There they found an environment rich in energy and volcanic chemicals, allowing them to congregate and thrive. The cells themselves are little changed, though their walls have become a bit thicker again due to the high pressure. The hexagonal cells easily tesselate to form continuous encrustations across the vents. These do not build up into cone shapes like the ancestral Protohydroia octherma, instead forming a flat layer, which may extend indefinitely until external forces intervene or their source of energy or surface runs out.
They spread by binary fission, both laterally along a surface and by splitting off free-floating cells. These free-floating cells derive from hextherma's dormant state. As they no longer needed to worry as much about barren areas or exposure to oxygen, this dormant state was no longer necessary for staying inert over many years. Instead, it's simply a stage in which they're a bit lighter and not stuck to anything, so they can drift through the open ocean from vent to vent and find a new suitable place to settle. Because population densities are so much greater, they also have much more opportunity for horizontal gene transfer and will often exchange genetic material with their neighbors.