The shell is of moderate size (maximum length 16.5 mm) and broadly fusiform. The spire is high and acute, consisting of two and one-half tightly wound, convex nuclear whorls and five moderately shouldered postnuclear whorls. The suture is deeply impressed. The body whorl is moderately large (more than one-half the total shell length) and broadly fusoid. The aperture is of moderate size and roughly ovate, with no perceptible anal sulcus. The outer apertural lip is barely erect and scalloped in a pattern reflecting the spiral sculpture of the shell; just behind the lip the varix is moderately developed into thin, sharp varical "wings" or flanges, the scalloping again corresponding to the shell's spiral sculpture. The columellar lip is smooth and entirely adherent. The siphonal canal is moderately long, narrowly open, and dorsally recurved.
The body whorl bears three bladelike varices. Spiral sculpture consists of seven weak cords on the body: these more prominent on the varices and ephemeral between them. The shell is pale waxy yellow-brown, covered by a moderately thick, flat-white, microscopically reticulate intritacalx. The aperture is porce-lancous pale brownish-white.

Known to us only from off San Carlos Bay, Sonora, Mexico, in 40 m or more.

Shell small, 6-varicate when adolescent, the mature whorl abruptly and sharply trivaricate, the intervals with a rather indistinct axial rib which in the final interspace fades to a weak shoulder-node; about 5 rude spiral ribs evident on the last turn which are best seen on the backs of the varices, the faces of which are even more strongly marked with ridges and alternating grooves. Aperture of moderate size, ovate; outer lip short, crenate, well calloused, bearing about 6 small, submarginal brown denticles; callus of inner lip narrow, sharply defined; canal rather long, very narrowly open at maturity, well recurved at tip. Periostracum absent; outer layer of shell whitish, chalky, easily breaking away to reveal an axial fibrillation and beneath that a fine spiral threading. Alt. of holotype 17.0, max. diam. 10.1, alt. of aperture 5.0 mm.

Type-locality: 15-35 fms., near entrance to Puerto San Carlos, Sonora;
Miss Margaret S. Cunningham (to whom this pretty species is dedicated for her kind help not only in this but in many other instances) May, 1963, & L. H. Poorman, Nov., 1963.

Comparisons: In general aspect the shell of this species most recalls a small Pteropurpura, but in texture and color it is more like certain species currently referred to Aspella. From the generitype of Aspella however, it is surely sufficiently distinct in both form and sculpture to warrant generic separation. One suspects that its nearest known relative may be "Aspella' indentata (Carpenter). Even these two seem hardly congeneric, resembling one another in little beyond the chalky outer layer of the shell.

Berry (1964), in describing this species, made it the type species of a new genus, Trialatella. Although differing in species-level characters, D. cunninghamae does not differ generically from such forms as D. myrakeenae.