Echinocereus rigidissimus

This is the less popular E. rigidissimus proper. It grows larger and has thicker spines than var. rubispinus and has same great flowers.

Sclerocactus wrightii

Young plant blooming at Capitol Reef National Park.

Epithelantha micromeris

Epithelantha micromeris at Carlsbad Caverns National Park.

Echinocereus engelmanii at the edge of Marble Canyon, AZ

Ferocactus sinuatus

This nice easy species is common in Trans Pecos region of Texas.

Acanthocalycium thionantum

Mammillaria viridiflora