Type locality. — Minerio, 35-41 m, in sandy sediments, Sao Tome Island.
Description. — Shell very small and fragile, almost transparent. Protoconch with 1 1/8 whorl, a diameter of about 150 µm, relatively large for the genus, beginning with a very small nucleus (about 20 µm). Teleoconch up to 5-5,5 convex whorls. The first half whorl is sculptured by about 8 spiral irregular cordlets. In the following whorls the upper part of the whorl (about 30%) is separate by a clear change of the microsculpture of the lower part: iin which it consists in predominant oblique opisthocyrt growth lines crossed by spiral striae, limited by a scarcely prominent shelf separating this part of the rest of the lower part of the whorl, which have curved lines in the prosocyrt sense. On this lower part of the whorl these lines are crossed by about 7-10 very evident spiral cordlets and some more near the base. Aperture rounded, umbilicus narrow. Dimensions: Holotype 1.3 mm high, being one of the largest shells examined.
Distribution. — Only known in Sao Tome and Principe Islands.
Etymology. — The specific name refers to the island where the holotype has been collected.
Remarks. — Murchisonella spectrum has a larger shell, with an evident separation between the two parts of the whorls: the spiral sculpture is formed by grooves instead of cordlets. Murchisonella africana spec. nov. has a similar protoconch, but the microsculpture of the first whorl of the protoconch is very different with very fine striae crossed by fine and numerous growth lines, and the lower part of the whorls have a very different microsculpture with only furrows instead of cordlets.