See text Megasurcula is a genus of medium-sized predatory sea snails, marine gastropod molluscs in the family Pseudomelatomidae, a family previously lumped with others collectively known as turrids.

The surface is rendered somewhat rough by relatively fine, close-set and irregular spiral lines.

Megasurcula is a widely isolated and strongly characterized genus, belonging exclusively to the living fauna of the Pacific coast of North America as far as known at present.

It is, at the same time, a rather direct descendant of the extinct Bathytoma, but the species are of far larger size, carpenteriana being probably the largest or most ponderous Pleurotomid known.

The embryo, which is conoidal and multispiral in Bathytoma, has gradually lost some of its whorls, as shown in Megasurcula, which of itself would not be a generic character, but there is in Bathytoma a broad constriction of the body whorl below the convexity, forming a short stout beak, which is wholly unobservable in Megasurcula, and the aperture is much more capacious in the latter, with the anal sinus much larger and different in form and position.