Once again, I checked the cemetery records carefully, and find that there are two other THROOP's buried in the old Crystal Lake Cemetery (now called "Lake Avenue Cemetery"):
THROOP, Nathan C.; s/o ?&M; d. 12/27/1874; 13y10m
THROOP, Old Lady (this is what the cemetery records say--there is no tombstone) bur. 3/28/1893
Also, I'd like to mention that this cemetery lies in Algonquin Township, City of Crystal Lake.I believe you should show Thomas Billings as died in Algonquin Township (not to be confused with the town of Algonquin).