Sunken Hollow

• WWizards of the Coast2015-08-25
  Official Ruling
  Even though these lands have basic land types, they are not basic lands because "basic" doesn't appear on their type line. Notably, controlling two or more of them won't allow others to enter the battlefield untapped.
• WWizards of the Coast2015-08-25
  Official Ruling
  If one of these lands enters the battlefield at the same time as any number of basic lands, those other lands are not counted when determining if this land enters the battlefield tapped or untapped.
• WWizards of the Coast2015-08-25
  Official Ruling
  However, because these cards have basic land types, effects that specify a basic land type without also specifying that the land be basic can affect them. For example, a spell or ability that reads "Destroy target Forest" can target Canopy Vista, while one that reads "Destroy target basic Forest" cannot.

Rulings via Scryfall