How to select files that have no extension using powershell

I have a drive with lots of directories and files, some of which are broken and have no file extension. I would like to delete all of the files that do NOT have an extension. I have tried `gci | where {$_.extension -eq ""}` and `gci | where {$_.extension -eq "."}` and variations of those, but end up getting nothing or everything on the drive. If I look at the results of `gci | select Extension` the files show nothing for the extension, just like a directory, not sure where to go. Any help would be appreciated.