Chollas are a genus of cacti. Mostly found in the southwest United States, chollas are also 'found' in Central/South America and Australia.
Chollas are 'Cylindropunti' - meaning they have cylindrical stems. Not flat stems.
There are pencil chollas. Teddy bear chollas. Christmas chollas. jumping chollas. Cane chollas. Dog chollas. Silver chollas, diamond chollas.
Sometimes, you just find dead cholla. Everywhere. In abundance.