The major morphological distinction between D. millbayana and D. dunnei is the shape of their pseudobranchs. D. dunnei possesses a strongly developed pseudobranch with a narrow stem, while D. millbayana’s well-developed pseudobranchs (2) have featherlike lamellae with upward pointing tips (Lemche 1976). – – preliminary data – – suggests they are conspecific.” (Shipman & Gosliner, 2015).
In both species red marks on the cerata (1) are not confined to the tubercles.

Right: 1: polyp colony with scale. 2: magnified hydrotheca. 3: magnified gonotheca.