To simplify the expression \((19^4)^9\) using the Power Rule of Exponents, we apply the rule that states \((a^m)^n = a^{m \cdot n}\).
In this case, we have:
\[ (19^4)^9 = 19^{4 \cdot 9} \]
Now, we perform the multiplication \(4 \cdot 9\):
\[ 4 \cdot 9 = 36 \]
Thus, we can simplify the expression to:
\[ (19^4)^9 = 19^{36} \]
So, the simplified equivalent expression is:
\[ \boxed{19^{36}} \]