The treatment of the hair is according to the Buddhist tradition. Gautama, after his departure from the palace, drew forth his sword and cut off his long hair. The early Buddhist text Mahavastu mentions that the hair of the Siddhartha was cut off by the gods and carried to the Trayatrimsa heaven, where it was worshipped as a sacred relic. It is also said that they also carried away his turban. The short locks, following the tradition, are curled from left to right in the shape of snail-shell. In China and Japan they sometimes take the form of round beads or sharp spikes.
The representation of the Buddha must always have either the chignon or the protuberance on the skull which is presumably the seat of the manas or living mind (soul) of the Buddha. It is terminated by a round ornament (the jewel).
This protuberance (ushnisha) is the first and most important of the thirty-two superior signs of a Buddha and probably last acquired. In the Indian Buddhist texts and its manifestations in art, the Buddha at his birth or in the different episodes of his life before his Enlightenment, is not represented with the protuberance of the skull. It is not until he attained the Buddhahood under the Bodhi-tree that he is represented with the full-sized ushanisha. Some say that the ushnisha means 'turban', dressed hair. According to a Buddhist tradition followed by Indian artists, the hair of the Buddha should be in short curls falling from left to right and the protuberance should also be covered with the curls. The shape of the ushnisha varied somewhat in different countries. The ushnisha of the Nepalese Buddhas is sometimes surmounted by a ball (jewel) from which issues a flame. According to a tradition the Buddha caused to issue from his head a flood of glory composed of a hundred precious rays. In Tibet the ushnisha if often surmounted by a flaming pearl (Jewel or cintamani). It is also said that the protuberance of the skull is a sign of supernatural wisdom of a Buddha. Some scholars opine that the ushanisha was basically a coil of hair, which later took the form of a protuberance on the skull.
The artist has bestowed ample attention on the face too - its plastic treatment is soft, simple and abstract, and this has given it a graceful mellowness. The almond shaped half-closed eyes and softly closed lips imply a delicate smile. The facial expression is expressing an inner experience of purity, compassion (karuna). wisdom (prajna) -the supreme attributes of Enlightenment.
The long lobes of ears, three folds on the neck and chiselled lines of simple eyebrows are the external symbols of a yogin.
The face is round and has slight pointed chin.
This description by Dr. Shailendra Kumar Verma, Ph.D. His doctorate thesis being on the "Emergence and Evolution of the Buddha Image (from its inception to 8th century A.D)."