Petrocha notogaearepresents a new interstitial dorvilleid genus from subtidal medium coarse sands. With its distinctly neotenic characters, such as one pair of short palps, ciliary rings on all parts of the body, setigers with uniramous parapodia, simple capillaries, simple heterogomph falcigers and comparatively small size (1.2–1.4 mm), it shows close phylogenetic affinity to several other taxa of the Dorvilleidae, such asIkosipodus, Microdorvillea, ArenotrochaandPusillotrocha, which have only been described in the last four year