This head, carved in the specific Hebei white marble, probably depicts Kasyapa. Kasyapa is the most famous of Shakyamuni's disciples. He was a devoted follower who accepted Shakyamuni's clothes when the master died in Kukkutapada. Kasyapa continued to spread the teachings for the preparation of the Future Buddha, Maitreya. He died reputedly wearing Shakyamuni's clothes.
A close example, although carved in a different stone, is in the Victoria and Albert Museum, London, and illustrated in Hai-Wai Yi-Chen, Chinese Art in Overseas Collections, Buddhist Sculpture II, National Palace Museum, Taipei 1990, pl.133, p.138.