This is a monotypic genus and the cactus is Hildewintera aureispina. The picture below is the same name, but has cristata after the other bit. As you can see mine is in a normal pot, but the other cactus needs to go in a hanging basket as it has long stems that often drop to the ground. Their habitat is between Argentina to Uruguay and the temperture can drop to -2° centigrade (c. 28° fahrenheit). My cactus has not flowered, yet hopefully it will show soon.
Adromischus ~ Astrophytum ~ Cephalocereus ~ Cereus ~ Cyanotis ~ Echinopsis ~ Epiphyllum ~ Espostoa ~ Ferocactus ~ Frithia ~ Gymnocalycium ~ Haworthia ~ Lithops ~ Lophocereus ~ Mammillaria ~ Notocactus ~ Opuntia ~ Pilosocereus ~ Rebutia ~ Schlumbergera ~ Sedum ~ Sempervivum ~ Stenocereus ~ Sulcorebutia ~ Tephrocactus ~ Turbinicarpus ~ Weberbauerocereus