Shell conical, somewhat elongated, whorls flat or scarcely convex, with marked suture, fragile.
Protoconch with a little less than one whorl, the separation with the teleoconch being usually visible; diameter about 300 mu: nucleus about 125 mu; first whorl, about 250 mu. Spiral microsculpture with minute depressions. Teleoconch with about three or three and a quarter whorls, with some irregular, very depressed and scarcely visible spiral striae and slightly prosocline growth lines. Aperture slightly ovoid, with a small deviation of the border of the external lip in the place where the spiral cords ends; there is a continuous and narrow peristoma. Externally, it is not possible to see any thickening near the external border.
Dimensions between 1.6 and 1.9 mm in height.
Animal dark only on the dorsum of the head and between the eyes, with tentacles dark with a white line in the middle; the penis is folded on its base and sharp at the extreme, presenting two small prominences one to each side and sometimes a black line in the middle; the sole of the foot is white.
Operculum ovoid, translucent, with the nucleus a little lateral. The radula is typical of hydrobids, similar to that of the previous species although the cusps in the rachidian and lateral teeth are a little shorter and less numerous.
Habitat: Under stones (limestone) lying on a coarse sandy bottom; always on surfaces devoid of (macro) vegetation. This species coexists with 4 other freshwater gastropods: Theodoxus cf. fluviatilis (LINNAEUS, 1758), Potamopyrgus antipodarum (GRAY J.E., 1843), Ancylus fluviatilis (MOLLER O.R, 1774) and Physella acuta (DRAPARNAUD, 1805).

Belgrandia alcoaensis was considered as a subspecies by Haase (2000: 185) after having only examined one shell (paratype). In the present work, we have examined many specimens and consider it very different from the other Portuguese species due to the almost flat whorls, especially the last one, the prominent spiral cord and the lack of any axial thickening.
Belgrandia lusitanica, Belgrandia heussi and Belgrandia silviae spec. nov. may be distinguished by their deeper suture and more convex whorls, the last one not angulated, as well as the existence of a prominence or axial thickening on the external lip.

Like Belgrandia lusitanica and Bel-grandia silviae spec, nov., this species must be considered in high risk of extinction, due to its limited range. This risk was recently increased by human intervention on the bed of the Alcoa River, from near its spring down the stream to the center of the village of Chiqueda de Cima. In the course of the last sampling in the site (February-2008), only a few specimens were observed.