The shell is external and whitish-transparent in colour, usually with a rounded-elongate shape and raised spire. The opening is large. The shell is umbilicated. The shell surface is largely smooth, but may have faint growth lines. The length of the shell is about 3 mm.
The body is darkish brown in colour. The head shield is lobed towards the front, and the foot is rounded in the hind part and has a middle furrow. The eyes of this species are visible, and the snail can retract completely into the shell.
The radula consists of 29 rows of teeth with one inner lateral on each side and one central (rachidian) tooth. The outer lateral teeth are absent. The lateral teeth are plate-like and the central tooth carries denticles. The male reproductive system consists of a short unbranched prostate connecting to a short tubular penis chamber.
Occurs at depths of 10–804 m on stones, stones with hydroids and algae. This species has been found at temperatures below 0 ° Celsius on the Norwegian continental slope. Specimens have been reported from the stomachs of haddock (Melanogrammus aeglefinus). This is the only species of the genus Toledonia found in the northern hemisphere, as most species occur in Antarctica.
Occurs in Svalbard, Greenland, Iceland, the Barents Sea, the White Sea, the Laptev Sea, the East Siberian Sea, and from the slope north of the Norwegian Trench at 62° 30’ N.
Ohnheiser LT og Malaquias MAE (2014). The family Diaphanidae (Gastropoda: Heterobranchia: cephalaspidea) in Europe, with A redescription of the enigmatic species colobocephalus costellatus M. Sars, 1870. Zootaxa 6(3774): 501-522. http://zoobank.org/References/1C4C791C-09D7-4711-9D05-1ABE3DB24916 DOI: 10.11646/zootaxa.3774.6.1.