2 A records, 2 PTR records, just 1 IP - is this proper?

[Name withheld by request]

Hi:

Is DNS setup incorrectly for host 10.123.85.254, based in this?:

  $ dig -x 10.123.85.254 +short
  z7engs005.oursubdomain.ourdomain.com.
  tapemonkey.oursubdomain.ourdomain.com.
  $ dig z7engs005.oursubdomain.ourdomain.com a +short
  10.123.85.254
  $ dig tapemonkey.oursubdomain.ourdomain.com a +short
  10.123.85.254

In my limited experience w/DNS I thought that you could have only one
name returned when you do a "dig -X"; ie PTR records for a given IP point
to exactly 1 name.

I also thought you could have only one A record associated with a given IP address,
and that this A record defined the canonical name for the host.

--
thanks,
Tom