Nipple Cactus

I was excited about this find. This is growing wild in southern Idaho. It is hard to spot because it is a low smallish cactus. It gets its name from the resemblance to mammillary glands and in fact they often grow as two side-by-side plants. I saw some of those but they hadn't put any buds up yet (probably a good blip for later). Around here they are only about 2-3" in diameter and a few inches above ground.

Escobaria missouriensis (Sweet) D.R. Hunt var.