Bills of review and bills in the nature of a bill of review, are bills filed to obtain a modification or reversal of a decree made upon a former bill. If the decree has been signed and enrolled a bill of review is used; if the decree has not been enrolled a bill in the nature of a bill of review is the proper remedy. Bills of review and bills in the nature of a bill of review may be brought either on the ground of error apparent on the face of the record, or newly discovered evidence. In the first case the bill of review may be filed as a matter of right, but in the latter case, the consent of the court is first required.