The genus Notoliparis (family Liparidae) includes five species (one provisionally included) of the deepest known living fishes, distributed in four Southern Hemisphere trenches at depths from 5400 to 7554 m. A key to the species is included herein. The Kermadec Trench north of New Zealand has the deepest known species, N. kermadecensis. In 2011, seven specimens were collected in traps by the R/V Kaharoa at depths from 7000 to 7261 m. Another 41 Notoliparis were collected in 2014 at depths down to 7554 m. Examination of these individuals showed that seven represent a new species, and the others are N. kermadecensis, originally described in 1964 from five specimens taken by HMDS Galathea in 1952. At that time, the types were in such poor condition that the original description was of necessity incomplete; a redescription is included here. Examination of the new specimens showed that N. kermadecensis has several undescribed characters, including one that is apparently unique in the family.