There's a few hits for mate-dev in any search engine. And normally I'd be inclined to direct you "to the (correct) source", but in this case, that's Debian's flavor of the MATE.
So I can only assume they
- Removed the code
- a package is not installed
- other annoyance
and of course, I'm not a "Debian guy" so I'm not about to do an operation that groks out all the changes from 2 separate distros.
and any references I do have are solely Ubuntu-14-Trusty sourced (Hello LinuxMint 17.x)
And there's "this"
nugget:
MATE 1.8.1 is currently packaged for Debian 8 (jessie). MATE 1.12 is also available on Debian testing (“Stretch”) and unstable (“Sid”).
Maybe, your MATE is old'ish?