Just wondered if the strange, subterranean flying worm beasties have ever been described in more detail in any other publication? Like in any of Chaosium's COC source books or anything? Given that the Mythos seems populated by monsters that seem to be in a pissing contest for the most tentacles and most consonants per name (not that this is a bad thing, mind!), I thought Lieber's creations were a refreshing change.
i'm not aware of leiber's vermis volatilis appearing anywhere else, but you made an opening for me to plug this story i wrote, which uses a little bit of 'terror from the depths' in part 2. hooray!
A monkey riding a dog is probably the awesomest thing that could ever happen.
Contributors wanted! Fantastic Horror — Original Works of Disturbing Imagination