mount: unknown filesystem type 'linux_raid_member'
You should not mount it directly using mount. You need first to run mdadm to assemble the raid array. A command like this should do it:
$ mdadm --assemble --run /dev/md0 /dev/sdc1
If it refuses to run the array because it will be degraded, then you can use --force option. This is assuming you don't have /dev/md0 device. Otherwise, you need to change this name.
When this command is executed successfully, you can mount the created device normally using:
$ mount /dev/md0 /mnt/test