C. guernei has been found in the eastern Atlantic off Portugal and the Azores at a depth of over 1100m. It reaches a maximum size of approximately 8mm. While a basal disk is present, it is not as strong as the one on C vicina, a species with which it has been confused. There are about 8 teleoconch and 4 smooth protoconch whorls with numerous low, broad costae per whorl. About 6 or 7 raised spiral threads are present on each whorl. The aperture is oval and the outer lip is thin.
While this species has been found together with C vicina, it can be separated by the weaker basal disk, thin outer lip and the presence of raised spiral threads between the costae.