Peyotillo (Pelecyphora aselliformis)
Origin: Mexico (San Luis Potosí)
Scientific classification
Kingdom:Plantae
(unranked):Angiosperms
(unranked):Eudicots
(unranked):Core eudicots
Order:Caryophyllales
Family:Cactaceae
Subfamily:Cactoideae
Tribe:Cacteae
Genus:Pelecyphora
Species:P. aselliformis
From my collection.
Photo from 2017 to compare its super slow growing: flic.kr/p/22G3JfC
via Flickr https://flic.kr/p/25dih2R