Mammillaria decipiens - Bird's Nest
Long, soft tubercles with a few short spines on the ends. Can handle lower light than most cacti, likes bright indirect light and morning sun only. In the wild it grows under the shade of other plants. Puts out offsets from the base and can eventually form a clump. Thick tuberous roots. Puts out pretty little white flowers. Very sensitive to over-watering. Use very well draining soil mix, and keep it dry in the winter.
Your plant will be similar to the one in the photos.
Mostly shade, morning sun only
Needs vary through the year
Vivid Root Mineral Mix or similar
shown in 3.5" pot
Ships bare root. Pot and soil not included.