I'm agree with Cortinarius colymbadinus, but it's necessary to see spores and spore print color.

yes its Cortinarius sp. to check molecular characterization and use ITS primer 

Thank you for your support and suggestions. I think that it might be a dark form of Cortinarius uliginosus, then associated with Salix.

Look like  Cortinarius, is necesary spore print color....but  I'm not sure of the species...perhaps colymbadinus or cotoneus...

I would recommend you determine it by ITS1/ITS4  or EF4/Fung5 PCR techniques, for confirmation after the morphological study

This look like Cortinarius sp. but go for  rDNA sequencing for confirmation.

Probable Cortinarius limonius but a careful microscopy it is necessary for a correct determination

Hello, Gymnopilus sp. is another possibility. As it was pointed out, micro is absolutely necessary, if DNA analysis impossible..

if you found these specimens on wood...they should be Gymnopilus species. ...this is my idea!

I agree with Laine and Elia. Gymnopilus is a real posibility. Most of species of G. growth on wood. In my country we are studding G. pampeanus which growth on soil near the base of the trunk of Eucalyptus, probably associated to the roots

.

I am pretty sure this is not a Gymnopilus. It has not grown on wood. It is a Cortinarius.

You cannot be sure that it hadn't grown on wood...Roots hidden in the soil are good enough for Gymnopilus. Elsewhere, some of them are reported to grow on soil as G. flavus, for instance.... But obviously, a single lillte picture is of little use to get secure identification..

I don't understand this : ""Gymnopilus spp. never look so slender in architecture". There is a number of Gymnopilus that can be that splender,, and even more smaller and thin ! Habits are very variable, in this genus.

The fact that there is no veil to be seen in the picture could also be use to negate the possibility of Cortinarius, a genus with  veil, I guess...

By the way, I was just pointing out an alternate possibility to Cortinarius, no more! .With only one picture, nobody can pretend more than enumerating possibilities..

It is extremely difficult to tell a species from a picture, especially from a foreign country where species or habits may not exist or differ from what you are used to from your native country.

I think Cortinarius uliginosus is a good guess, although the colour of the velum belt is rather strong, and the stipe especieally on the left is rather thick for that species. I don´t believe this is a Gymnopilus. Identification from photos is often diffucult, often impossible, but if you know species, it can be made. Easiest way is just to do a squash preparation and look for the spores and other microscopic features. Funga Nordica (Nordeloos et al.) is the best option for keys. If you´re working with species of Cortinarius, I recommend Brandrud et al. Cortinarius Flora Photograpchica.

We have to remember, that every year new, undescribed species of fungi (basidiomycetes and ascomycetes) are found from even well known and studied areas, eg. Fennoscandia. Fungi are very poorly known, compared to plants and animals.

I agree with  Hanna, Identification from photos is often diffucult, often impossible,you need to have other data such as : study of spores (color , size) , hymenophore study, descriptions fresh mushroom .