Megasurcula carpenteriana (Gabb, 1865), also known as Carpenter's turrid,[3] is a species of medium-sized predatory sea snail, a marine gastropod mollusc in the family Pseudomelatomidae, a family previously lumped with others collectively known as turrids.

[5][2] Subspecies within this species include: The shell is small, in the adult stage averaging about 62 mm (2.4 in) in length, against 90 to 110 mm (3.5 to 4.3 in) in length for the fully adult carpenteriana.

The periphery is often marked by a minutely beaded or undulate thread, and is more nearly midway between the sutures on the spire than in carpenteriana.

The aperture is shorter than the spire in nearly every case, while the reverse is true of carpenteriana.

(description of Bathytoma tremperiana compared with Bathytoma carpentaria)[7] This marine species occurs from California, USA to Central Baja California, Mexico