Belemnitella mucronata; Print; Belemnitella is a genus of belemnite from the Late Cretaceous of Europe and North America. Belemnitella was a squidlike animal; probably related to the ancestors of modern squids and cuttlefish. The shell was internal. The rostrum or guard is found the most often and possesses a distinctive slit at its ventral surface and a ridge on the dorsal surface. The phragmocone (internal shell) has a small protoconch at its tip; and fit into the cavity and the guard. It also had septa and a ventral siphuncle (tube filled with living tissues running through chambers) within the phragmocone; projecting forward as a beak-like blade.