Missing mtio.h under Xenix V286

[Paul, Raymond & Tonnie]

I'm writing a tape device driver under Xenix 286. I have the complete
development system and link kit but I can't find the file mtio.h, not
in /usr/include and not in /usr/sys/h. I installed every single Xenix
floppy I have so I don't think that that is the problem. Could 
somebody please mail me this file or tell me where I can find it.
(I have already tried find . -name mtio.h -print)

Thanks
Paul Derks
blitter at ele.tue.nl