A word of explanation may appropriately be added here of the expression _wu-ni yao_,[283] which occurs in several passages in Chinese books on pottery. It means "black clay ware," and as a general term would naturally include the "hare's fur bowls." Indeed, one passage[284] actually speaks of the _wu-ni yao_ of Chien-an, and the _T´ao lu_, which gives the ware a paragraph to itself, states that it was made at Chien-an, in Chien-ning Fu, beginning in the Sung dynasty, and that its clay was black. It further adds that the glaze is "dry and parched" and that it was sometimes green (_ch´ing_). It is clear from the above quotations that _wu-ni yao_ was a general expression for the dark-bodied Chien ware; and there the matter would have ended had not early works, such as the _Cho kêng lu_ and _Ko ku yao lun_, mentioned it in the category of Kuan and Ko wares, the former naming it with the Hsün and Yu-hang wares, which were inferior to the Kuan, and the latter adding to the passage dealing with Kuan wares the following note: "There are black wares which are called _wu-ni yao_, all of which were imitated at Lung-ch´üan. They have no crackle." The _Po wu yao lan_, however, explains that these wares "were admitted _by confusion_ into the category of Kuan and Ko wares," and that the "error has been handed down to this day." Probably it was the green variety which caused the confusion, as there seems no reason why the black glazes should have been associated with the Kuan class, though the dark red clay of the Phœnix Hill from which the Hang Chou Kuan ware was made may have had some resemblance to the dark red brown body of the Chien yao. As for the Lung-ch´üan imitations, we can only imagine that the statement refers to the later Ko wares, which are said to have been made with material brought from Hang Chou,[285] and that their glaze, too, was of the green variety, as would be expected in the Lung-ch´üan district, the home of the green celadons. At the same time it will be remembered that _wu-ni yao_ means simply "black clay ware," and might have been fairly applied to any dark-bodied ware wheresoever made.