Port mapping services

[Brett Glass]

I'm doing some research on port mapping services -- services that map protocol
and program names to IP port numbers -- and have come up with a question I'm
having trouble answering.

What is the difference between the "portmap" service (generally offered on 
TCP port 111) and the "loc-srv" (or "epmap") service that many machines seem
to offer on TCP port 135? Are they merely the same service offered on
different ports? Is the service offered on port 135 an enhanced or proprietary
version of the one offered on 111?

--Brett Glass