Missing table suffix in data directory directories

[Jason Kania]

Hello,
In the data directory of my 3.0.9 installation, I have directories with both 
suffixes and without:
periodicReading
periodicReadingTemp-76eb7510096811e68a7421c8b9466352
The directories with and without suffixes are being updated and for those with 
a suffix, the suffix matches the output of this command:
SELECT keyspace_name, table_name, id FROM system_schema.tables ;
Can someone indicate why some would have suffixes and others not?
Thanks,
Jason