Mammillaria nivosa

Mammillaria nivosa is a species of cactus also known by the name woolly nipple cactus and is native to the Caribbean.

Description
Mammillaria nivosa is radially symmetrical and can grow up to 25 cm tall. It has spines that can grow to about 38 mm and often overlap, probably to make it difficult for large organisms to reach the flesh of the cactus.

The plant produces yellow flowers that are approximately 15 mm long.