Question: Which is a type of cactus, Espostoa or Cryptanthus?
Context: Pobiti Kamani (Bulgarian: Побити камъни , "planted stones"), also known as The Stone Desert, is a desert-like rock phenomenon located on the north west Varna Province border in Bulgaria.  It is considered the only desert in Bulgaria and one of few found in Europe.  The desert consists of sand dunes and several groups of natural rock formations on a total area of 13 km².  The formations are mainly stone columns between 5 and 7 meters high and from 0.3 to 3 meters thick.  The columns do not have solid foundations, but are instead hollow and filled with sand, and look as if they were stuck into the surrounding sand, which gives the phenomenon its name.  Sandstorms and sand twisters have also been known to commonly occur in this desert region of Bulgaria.  The Stone Desert is not only a well known European tourist attraction due to its desert like habitat, but it is one of few places where desert type vegetation such as cactus are known to grow.  It is also the only desert in Europe in which desert reptilians and other desert type animalia are found to thrive.  The Stone Desert along with the Tabernas Desert of Spain is one of two naturally formed deserts in all of Europe and the only known naturally formed desert in Eastern Europe. Pediocactus sileri is a rare species of cactus known by the common names Siler's pincushion cactus and gypsum cactus (or gypsum plains cactus).  It is native to southwestern Utah and northwestern Arizona in the United States.  It is limited to a specific type of soil, individuals are often spaced far apart, and the species is threatened by a number of human activities such as off-road vehicle use, poaching, and uranium mining.  This is a federally listed threatened species of the United States. Pediocactus bradyi is a rare species of cactus known by the common names Brady's pincushion cactus, Brady's hedgehog cactus, and Marble Canyon cactus.  It is endemic to Arizona in the USA, where it is restricted to Marble Canyon in Coconino County.  It is limited to a specific type of soil, it has a small distribution, and the species is threatened by a number of human activities.  This has been a federally listed endangered species of the United States since 1979. Pseudomonas excibis is a gram-negative, rod bacterium first isolated from the gastric caeca of the cactus bug ("Chelinidea vittiger").  The type strain is ATCC 12293. Espostoopsis is a monotypic genus of cactus containing the single species Espostoopsis dybowskii.  The generic name is formed from Greek "opsis" meaning "view", referring to its resemblance to the genus "Espostoa", with which it is often confused.  The plant is only known from northern Bahia, Brazil. Mammillaria mammilllaris, common name Woolly Nipple Cactus, is a species of plant in the Cactaceae family.  It is the type species of the genus "Mammillaria".  It has been described by Carolus Linnaeus as "Cactus mammillaris" in 1753.  The specific epithet "mammillaris" comes from the Latin "mammilla", meaning "nipple", with reference to the characteristic tubercles. Cryptanthus is a genus in the botanical family Bromeliaceae, subfamily Bromelioideae.  The genus name is from the Greek “cryptos” (hidden) and “anthos” (flower).  This genus has two recognized subgenera: the type subgenus and "Hoplocryptanthus" .  All species of this genus are endemic to Brazil.  The common name for any "Cryptanthus" is "Earth Star". Espostoa is a genus of columnar cacti, comprising 16 species known from the Andes of southern Ecuador and Peru.  It usually lives at an altitude of between 800m and 2500m.  Its fruit is edible, sweet, and juicy.  The genus is named after Nicolas E. Esposto, a renowned botanist from Lima. Creosote bush scrub is a North American desert vegetation type (or biome) of sparsely but evenly spaced desert plants dominated by creosote bush ("Larrea tridentata") and its associates.  It's visual characterization is of widely spaced shrubs that are somewhat evenly distributed over flat or relatively flat desert areas that receive between 2 and 8 inches of rain each year.  It covers the majority of the flat desert floor and relatively flat alluvial fans in the Mojave Desert, Chihuahuan Desert, and Sonoran Desert.  The dominant plants that typify this vegetation type are creosote bush ("Larrea tridentata") and its associates, white bur-sage ("Ambrosia dumosa"), brittlebush ("Encelia farinosa", "Encelia actoni", "Encelia virginensis"), cheese-bush ("Ambrosia salsola"), Mojave yucca ("Yucca schidigera"), silver cholla cactus ("Cylindropuntia echinocarpa"), and beavertail cactus ("Opuntia basilaris").  Creosote bush has a wider range than its associates, so codominant shrubs, which are associated with more narrow ranges, will vary from region to region. Mammillaria spinosissima ( ), also known as spiny pincushion cactus, is a type of cactus endemic to the central Mexican states of Guerrero and Morelos, where they grow at elevations of approximately 1600 to 1900 meter .  The species was described in 1838 by James Forbes, gardener of the Duke of Bedford.  Botanist David Hunt collected a specimen in 1971, when he located one near Sierra de Tepoztlan, Mexico.
Answer: Espostoa