Since the ONS M-series cards are not supported devices under CiscoWorks LMS (reference: http://www.cisco.com/en/US/docs/net_mgmt/ciscoworks_lan_management_solution/3.2/device_support/table/lms32sdt.html), you'll need to:
a. delete them from your Device and Credentials Repository (DCR). Do this via: Common Services > Device and Credentials > Device
Management.
b. change your discovery options to make sure they are not rediscovered / re-added. Depending on your setup, how to do this varies. If you are doing automated discovery in LMS, go to: Common Services > Device and Credentials > Device Discovery > Discovery Settings and configure a filter. SysObjectID may be a good filter option in this case.
If you are running in ACS mode, I'm not sure you can delete the devices in LMS without also deleting them in the ACS server. That might affect your AAA procedure for your devices.