Flauto Dulcio is listed only by Wedgwood, who says: (Lat.) Dulcis = sweet. 8 ft.; 4 ft. According to Seidel, an open wood Flute register, of small scale, with a sweet pleasant tone. Schlimbach states that it is practically a small-scaled Offenflöte. Flauto Dulcio is also a synonym for Flauto Dolce.
See Flauto Dolce for examples of Dulzflöte. No examples of Flauto Dulcio or Flauto Dulcis are known. Contributions welcome.