Wikipedia
Stroboceras
Stroboceras is an extinct nautiloid named by Hyatt in 1884 that's included in the nautilid family Trigonoceratidae; the group that have rise to the Nautilidae which includes the living Nautilus.
Stroboceras is characterized by a loosely coiled evolute shell bearing prominent longitudinal ridges and grooves; with a variable cross section, generally higher than wide, flanks convergent on the venter, and a subcentral siphuncle.