Can't mount old CD-ROM - ISO-13346 UDF format

I have an old CD-ROM I'm trying to read using my external USB drive. After some time spinning, it mounts with a README.TXT file containing the text:

This disc contains a "UDF" file system and requires an operating system that supports the ISO-13346 "UDF" file system specification.

I've tried mounting using mount -t udf and mount -t cd9660 but neither work. Any suggestions?