The synonymy of Caecum clarkii Carpenter, 1858 (Gastropoda Prosobranchia: Caecidae) is most bewildering. In 1858 Carpenter described two species from the Canary Islands, viz. C. clarkii and C.pollicare. These species were distinguished by the fact that C. clarkii has a completely smooth outer surface while in C. pollicare the outer surface shows (p. 433) “irregular longitudinal corrugations resembling thumb-marks”. Carpenter (p. 433) explicitly states “in shape agreeing with clarkii”, so the “sculpture” is the only difference. Now it is known that many Caecidae have a very thin periostracum which is not easily discerned even under the microscope. Thus it might well be that the “sculpture” described by Carpenter is nothing else than the surface structure of the thin periostracum. Moore (1974, in litt.), after having examined some specimens from Gran Canaria (Van Aartsen collection) even is inclined to think that C. clarkii, C. pollicare and C. vitreum Carpenter, 1858, all are in fact the same species. This conclusion however, was not based on actual specimens of C. vitreum which in our opinion is clearly different.