(for more information about Ultrix, see the Wikipedia article).
Ultrix (officially all-caps ULTRIX) was the brand name of Digital Equipment Corporation's (DEC) native Unix systems. While ultrix is the Latin word for avenger, the name was chosen solely for its sound.
There were two variants of Ultrix: Ultrix-11 which ran on the PDP-11 family, and Ultrix-32 which ran on the VAX platform. This version is Ultrix-11.
The files here come from the Ultrix 3.1 area of the Unix Archive, and were donated by Steven Schultz.