http://www.cactus-art.biz/schede/TOUMEYA/Toumeya_papyracantha_hybrid/Toumeya_x_knippelianus/Toumeya_papyracantha_x_Echinocereus_knippelianus.htm
here is an trully remarkable inter-generic hybrid between Toumeya and E. knippelianus. (unconfirmed). very unusual looking plant.

as a coincidence, both these plants in my collection are budding now:
interestingly both these plants seem to flower at the same time and the buds are similar and red.

Toumeya:


E.knippelianus:


now to wait for flowers to develop and open and attempt to cross pollinate. i'll try both ways. lets see if i can replicate.

The result doesn't really look like cross between the two but its worth a shot.

it has been argued that the said hybrid plant is some form of unknown monstrose mammillaria, or a mammillaria hybrid, or another intergeneric hybrid involving a mammillaria and another cactus, based on the notion that the two supposed parents are too distant for a cross to be possible and the flowers are borne in a ring around the plant (like mammillaria).

granted, it does have the thick fleshy roots of the E.knippelianus (which are incredibly pink!), flat spines like Toumeya (a very uncommon feature for mammillaria), as well as white radial spines and large white areoles like toumeya.

yep well in any case it is worth a shot.