The three 3-polyiamonds are called tetriamonds.
Tetriamond
See also
PolyiamondExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Tetriamond." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Tetriamond.html
The three 3-polyiamonds are called tetriamonds.
Weisstein, Eric W. "Tetriamond." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Tetriamond.html