Euthria darwini is characterized by a small, rather heavy shell, sculptured with big, broad spiral cords, spire whorls with 5 or 6 cords, body whorl with about 18 such cords. Al shells we studied have a greyish and eroded surface, consequently the pattern are colour are hard to detect.

Description: Shell ovoid-fusiform and solid. The protoconch only preserved in the holotype) is whitish, with 1 and 2 spiral whorls and a diameter of about 1.2 mm. Teleoconch with about 4-5 rapidly increasing whorls. The shell has axial ribs on the first whorls, which disappear on the last one. Spiral cords are evident, 5-6 on first whorls, and on the last one 7 up to the periphery and 11 more up to the base. Subsutural ramp slightly depressed. Aperture ovoid, white, with 9 internal lirae visible at the inner part of the peristome; it is continued as a narrow and slightly curved siphonal canal. Whitish-cream ground colour, in some places with small axial separated flammules. Holotype 27.6 mm x 13.2 mm. The paratype is 29.9 x 14.3 mm. Soft parts unknown.

Some shells of Euthria calypso, in this case the ones that have well developped spiral cords on the last whorl, look similar but differ by the higher number of spiral cords and the larger adult size.

The shells under study here were presented in Rolan (1987), fig. 5 as E. adeles. The paratype slightly differs from the holotype in the number of spiral ribs, which are more numerous (up to 23 on the last whorl instead of 18 in the holotype), and it has 8 internal lirae in the aperture (instead of 9).
The present species must be compared with those with spiral sculpture:
* Euthria adeles Dautzenberg & Fischer, 1906 is white with brown dots or partly brownish, the axial sculpture is formed by few wide ribs, which are present in the last whorl, the suture is more marked and the whorls more convex, the protoconch is darker.
* Euthria calderoni Rolan, 1985 is variable but always coloured, smaller and narrower, with a more elongated shell, and numerous short wide axial ribs on the last whorl. The interior of the aperture is either brown or of the same colour as the shell.
* Euthria helenae Rolan, Monteiro & Fraussen, 2001 is larger, with more convex whorls, short and wide axial ribs and dark color on the apex and in the base.
* Euthria abrotona Fraussen & Rolan, 2003 is larger, yellowish, and the spiral sculpt s only formed by small lines.

Cape Verde. Known from off Boavista Island (type material) and one additional specimen from off Sal Island (Palmeira, in lobster trap at 100-120 m, FS).

Type locality: South of Boavista, 3 miles off Curral Velho, Cape Verde Archipelago. About 50-75 m. The species is only known from the type locality. The short protoconch suggests an insular endemism.