The only species of Mohnia Friele, 1879 (Caenogastropoda, Buccinoidea, Buccinidae) in the North Pacific represents an unrecognized new genus of Newtoniellidae (Triphoroidea).

Mohniakurilana Dall, 1913 was described more than 100 years ago from deep waters off the Kuril Islands and remains exceedingly rare in museum collections. Originally placed in the carnivorous neogastropod family Buccinidae, fragmentary soft parts from the type lot and from several specimens belonging to allied species collected in the Aleutian Islands in the 1990s have allowed anatomical investigations for the first time. These have revealed the presence of a paucispiral operculum with an eccentric nucleus, foot with a deep propodial pedal gland and metapodial pedal gland, taenioglossate radula, short acrembolic proboscis, well-developed mid-esophageal gland, glandular prostate, and the absence of a penis; the nervous system is epiathroid with a long supra-esophageal connective and numerous statoconia in the statocysts. Analysis of the gut contents revealed abundant halichondriid sponge spicules. This evidence indicates a placement in the Triphoroidea, a diverse superfamily of specialized spongivores. Mohniakurilana is transferred to the Newtoniellidae and placed in the new genus Pseudomohnia gen. nov. Pseudomohniarogerclarki sp. nov. is established for a new species from the Aleutian Islands characterized by its narrowly turreted shell and distinctive multicuspid rachidian. A lectotype is designated for Mohniakurilana.