Euthrio calypso displays a high variability and is hard to define. The shape is usually moderately slender with a high spire; the whorls are laterally flattened and have a weak sub¬sutural concavity that may be somewhat more accentuated in sculptured specimens; the protoconch has about 2 whorls; the first two whorls have 10 or 11 axial ribs that become much weaker or absent along the third whorl; the spiral sculpture consists of 3 or 4 fine spiral cords on first teleoconch whorl; the teleoconch and body whorls are usually smooth but occasionally have broad but weak spiral cords; the length of the siphonal canal is varying from moderately short (holotype) to moderately long.
The pattern is quite pale, with small red-brown, rectangular blotches, neatly arranged in narrow spiral bands; separated by narrow interspaces, ranging in width from a fine line to slightly broader than the spiral band; aperture snow white. The tip of the siphonal canal is usually white (holotype) or may have some brown striked.
Many specimens show a broad, more densely patterned, spiral band along midwhorl. In the much darker patterned specimens this band, but darker, is situated on exactly the same place. Also the subsutural band may vary from a limited number of small spots, over more but still small spots (holotype) and larger spots, to a moderately dark band interrupted by a limited number of white dots. Occasionally the subsutural band is, together with the narrow spiral bands along the whorl, almost continue.

Euthria amorimi differs from E. calypso in its sculpture of numerous, fine spiral threads along the spire whorls and , usually, also along the last whorl; the usually weaker subsutural concavity and its slightly smaller adult size. The pattern of E. amorimi consists of narrower spiral lines that are rarely interrupted on a yellowish background. Euthria darwini differs from E. calypso, and in particular the ones with spiral cords, in its lower number of spiral cords (4 or 5 on the penultimate whorl and about 18 on the last whorl) and a smaller adult size.

Cape Verde. In moderately deep water (100-200 m) off Sal and Boavista Islands.