The Weyl geometry, as modified by Dirac, can lead to the presence of a field consisting of bosons of spin 1 and finite mass. It was proposed earlier that these bosons, called weylons, form the bulk of the dark matter in the universe. The development of this Weylian dark matter is investigated from the time of its creation until the present, and an acceptable cosmological behavior is obtained. One finds that this dark matter was unimportant in the early stages of the universe but became important at the time of galaxy formation and may have played a role in this process.