vishalbhave's Identifications

The position and nature of the gills would appear to be characteristic. In D. nigra the gills are relatively numerous and form a compact circle around the anus at the extreme posterior end of the dorsum. In D. fumata there are only 5 or 6 gills which are relatively large and openly branched. Unlike D. nigra they are situated in the dorsal midline some distance from the extreme posterior end of the body.

Source: http://www.seaslugforum.net/find/dendnigr