Shell small, solid, fusiform, almost biconical. Protoconch smooth and shiny, chest¬nut colored, with a nucleus of about 120 µm and a diameter of about 450 um. Teleoconch usually with 4-4,5 whorls bearing a coarse sculpture of axial ribs, numbering 12-15 on the first whorl, 18-22 on the second and about 28 - 35 on the last one. These ribs are crossed by three spiral cords on the first whorls and 18-20 on the last. The crossing of ribs and cords gives the shell a reticulated aspect. Aperture elongate axially, columella opisthocline, with 2-3 small denticles; on the inner part of the external lip, there are about 10-12 small teeth, some of them more prominent. Colour brown and white: brown on the subsutural area and in the lower part of the last whorl below the periphery. A band just on the separation of these two parts is formed by blotches of brown and white. Towards the base, the brown colour is reduced to small rectangles on the spiral cords. In some shells a similar line can also be seen on the upper part of the shell.
Dimensions: Holotype is 4.5 mm; specimens may perhaps grow to be a little larger, but most of them are smaller, even between 3.3-4.0 mm

In ROLAN & BOYER the present species was figured as a morph of M. saotomensis. At the time, not enough material had been examined. Today, after having the opportunity to study more shells, we can point out the constancy of morphological differences with M. saotomensis. This and the isolation of both populations on two islands many kilometers apart, convinced us that M. hernandezi is a valid different species.
Mitromorpha saotomensis has a shell which is larger in size, darker, almost black, very dense sculpture of axial ribs and spiral cords.
Mitromorpha monodi (Knudsen, 1956) is larger, whitish on the upper part, the protoconch is white, and it is endemic to Senegal.
Mitromorpha wilheminae Aartsen, Menkhorst and Gittenberger, 1984 is larger and wider, with a similar colour, but the axial sculpture is faded; more-over, it is endemic to the Mediter-ranean.

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