- rock elm, Ulmus thomasii - tall widely distributed elm of eastern North America
--1 is a kind of elm, elm tree
--1 is a member of Ulmus, genus Ulmus - American elm, white elm, water elm, rock elm, Ulmus americana - large ornamental tree with graceful gradually spreading branches common in eastern North America
--2 is a kind of elm, elm tree
--2 is a member of Ulmus, genus Ulmus