Hallo Bernardino,

Colus gracilis and Colus jeffreysianus are obviously heavely to
distinguished.
Look also in SABELLI & SPADA (1985): "Guida illustrata all'identificazione
delle Conchiglie del Mediterraneo" - Supplemento at Boll. Malac., XXI (1-4,
G.I. 21, where the authors also present the two shells erroneously
different.
I have not seen any of the two species from the Portuguese coast.
I have my hints to the spread there also only from the works by BOUCHET &
WARÉN, NOBRE and ROLÁN MOSQUERA & PEDROSA, and it is absolutely possible
that the determination with NOBRE is not correct, especially since he
localizes Colus gracilis in Portugal only very broadly and doesn't speak of
Colus jeffreysianus at all.
BOUCHET & WARÉN restrict the spread of Colus gracilis to the south until "N
Portugal".
With greetings,
Gert