Four species are known in Europe. Fruitbody boletoid with partial veil, leaving a fibrillose ring. Cap fibrillose scaly. Stipe hollow or solid. Tubes decurrent (running down the stipe). There is strong molecular evidence that this genus must be integrated in Suillus; here for practical purposes, I would prefer to list it as a genus on it own. Note also that the genus Fuscoboletinus is also kept separately, although it also must be integrated in Suillus.
Boletinus spectabilis (Peck) Kuntze
Unknown to the author. Cap with coarse reddish brown large scales. Stipe cylindrical, solid, whitish or concolorous with the cap, below the tubes with fibrillose ring. Flesh yellow, slowly staining pinkish then brown when exposed to air. Tubes short, decurrent, yellow. Pores large, angular, yellow, usually staining pinkish when bruised. Smell disagreeable. Taste unpleasant. Spores 9–15 × 4–6.5 μm.
Habitat. Mycorrhizal with larch (Larix).
Distribution. In Europe only known from Finland and Russia (Perm Krai).
I am not yet hosting photographs of this species, but I would suggest that you may take a look on the links below.
Engel, H., Dermek, A., Klofac, W., Ludwig, E. & Brückner, T. 1996. Schmier – und Filzröhrlinge s. l. in Europa. Die Gattungen Boletellus, Boletinus, Phylloporus, Suillus, Xerocomus. Verlag Heinz Engel, Weidhausen b. Coburg.
Korhonen, M. 1991. [Fuscoboletinus spectabilis, a new for Europe bolete, found in Finland]. – Sienilehti 43: 6-8. [In Finnish]
Knudsen, H. & Vesterholt, J. [eds.]. 2008. Funga Nordica. Nordsvamp, Kopenhagen.
Murrill, A.W. 1914. American boletes. Published by the author, New York.
Peck, C.H. 1873. Report of the Botanist (1869). – Annual Report on the New York State Museum of Natural History 23: 27–135. (available online in various formats)
Smith, A.H. & Thiers, H.D. 1971. The boletes of Michigan. The Univesity of Michigan Press, Ann Arbor. (available online)
Переведенцева, Л.Г. 1999. Биота и экология агарикоидных базидиомицетов Пермской области. Диссертация на соискание ученой степени “доктор биологических наук”. Москва. [Perevedenceva, L.G. 1999. Biota and ecology of the agaricoid basidiomycetes of Perm Oblast. Doctoral thesis.] (abstract in Russian available online)