Shell small, solid, fusiform, almost biconical. Protoconch smooth and shiny, pink coloured, with a nucleus of about 150 µm and a diameter of about 410 pm. There is a kind of blunt angle on the subsutural part. Teleoconch usually with prominent nodulous spiral cords crossed by axial ribs forming nodules at the intersection points. There are three of these spiral cords on the first whorls and on the last whorl, below the end of the spire, there are 9-13 additional cords, with slightly smaller nodules. There are 13-16 axial ribs on the first whorl, and
13-20 on the subsequent ones. Aperture narrow and elongate, columella opisthocline, almost straight and with very small teeth in the middle. On the inner part of the external lip there are 7-9 small teeth, of which the second on the upper part is larger and more prominent. Colour pink with lighter nodules on the upper part of the last whorl and darker on band which continues the suture, and in some points more. Towards the base, the colour is lighter.
Dimensions: Holotype is 4.3 mm, like most of the paratypes.

Mitromorpha annobonensis was figured in ROLAN & BOYER (2001: figs. 26-27, 41 and 43) as a form of M. saotomensis Rolan & Boyer, 2001. At present, after a careful compari¬son, we can state that they are different species. It must be distinguished from the closest species by the spiral angle of the protoconch which was not found in any other species. Other morphological differences are:
M. saotomensis is darker, almost black; the number of spiral cords on the whorls is higher (21 to 30 on the last one). Also the axial ribs are denser; the protoconch is rounded, lacking any angle and presenting micro tubercles.
M. monodi (Knudsen, 1956) is larger and the upper middle part of the shell and the protoconch are whitish.
M. hernandezi lives in sympatry and is smaller, more densely sculptured in axial ribs and spiral cords, the upper part of the last whorls is lighter with separation from the lowest dark one.

Guinee-Bissau. Only known from Annobon, from where it is supposed to be endemic.