The shell is of moderate size (maximum length 35 mm) and broadly fusiform. The spire is high, consisting of one and one-half nuclear whorls and six or rarely seven weakly shouldered postnuclear whorls. The suture is shallow and undulate. The body whorl is large and broadly fusoid. The aperture is moderately small and ovate to lenticular, with a narrow, moderately shallow anal sulcus, delimited to the left by a weak transverse ridge. The outer apertural lip is thickened, barely erect, and broadly crenulate, its inner surface bearing five weak, elongate denticles. The columellar lip is smooth, moderately thickly callused, and completely adherent, with a faint, oblique indentation just above the top of the canal. The siphonal canal is moderately long, straight, narrowly open, and weakly, dorsally recurved.
The body whorl bears two expanded, more or less spinose varices, these situated opposite each other on the ventral surface of the shell. Additional axial sculpture consists of two or three knobs at the shoulder margin. Spiral sculpture consists of ten or 11 moderately strong cords, these evenly distributed over the shell from the shoulder margin to the midpoint of the siphonal canal, the top three or four cords ephemeral between varices, the uppermost five or six spiral cords developed on the varices into short, sharp, dorsally recurved spines. A webbing, thick at its base and thin at the varical margin, connects the spines and produces a winglike varix. The leading edge of the varix is tightly laminate, with narrow grooves extending from the varix to the ventral surfaces of the spines.
Shell color is gray-brown, with pale tan varices, gray-brown spiral cords, a white apertural margin, and a darker purple-brown stain at the tip of the siphonal canal.

This species has been confused with Eupleura triquetra Reeve, 1845, many workers considering the two synonymous. Others have applied names to forms without reference to the original figures (the types have not been located in recent years), resulting in mistaken identity. The adult E. muri-ciformis has a broadly trigonal, flattened shell with expanded varices, and the shell color is predominantly brown, whereas E. triquetra has a more narrowly trigonal, unflattened shell with essentially unexpanded varices, and the shell color is predominantly blue-gray. Significant radular differences corroborate these shell distinctions.

Southern Baja California (Tsla Cedros to Cabo San Lucas) and the Gulf of California to Ecuador.