Extensive air showers with the small muon content in the region of ultrahigh energies

Ultrahigh-energy extensive air showers registered at the Yakutsk EAS array have been considered. The showers without the muon component are detected. Almost one half of them forms the clusters, the arrival directions of which correlate with the nearest pulsars. The classification of showers by muon composition has been carried out and the existence of four classes of showers has been shown. The problem of mass composition and origin of ultrahigh-energy cosmic rays are discussed.