A shelled, uncoiled, pyramidally shaped, pelagic snail. The posterior footlobe is very large [C.andreae-sp].
Shell straight, except for the posterior point which abruptly curves dorsally, it is slender and thin [C.andreae-s]. The ventral side is somewhat more convex than the dorsal side. Lateral ribs well developed, straight and regularly diverging [C.andreae-lr]. The longitudinal ribs on dorsal and ventral sides and the transverse striation are faint or absent, both sides are flattened. The rear angle of the shell is small. Near the aperture the shell width is about one half to one third of the total shell length. The embryonic shell is separated from the rest of the shell by a clear ring. The embryonic shell is round without a terminal cusp, and curved ventrally in regard to the caudal point of the shell.
Radula formula: 1-1-1.
Juveniles provided first with a perfectly round protoconch I that later grows out with the broad cylindrical protoconch II. A small cusp is sometimes present at the posterior tip, but this is quickly worn off. Protoconch II does not have growth lines close together as in the order Gymnosomata.
Soft parts are dark brown to black.
The shell measures up to 20 mm long, and is 5 times as long as broad.
Adults bathypelagic; juveniles live at shallower depth in the upper 200 m.
Clio andreae is a good swimmer that feeds on phytoplankton and protozoa; juveniles are also phytophagous.
Distribution in the North Sea
Might occur in the northern North Sea as a guest from the NE Atlantic.
Atlantic Ocean between 60°S and 75°N, common in the N-Pacific Ocean.
[After Van der Spoel et al., 1997]