However, the most important relic in the chapel is an inscription and a drawing of a merchant boat on a stone (25 x 12 inches) by a Christian pilgrim made either before Constantine built the Church (ca. 330 AD) or when it was under construction. Excavated in 1971, this stone carving is perhaps the earliest known Christian art discovered from the Holy Land (some even propose a 2nd century AD date to the drawing). The inscription in Latin is generally read as ' DOMINE IVIMUS' or 'Lord, we will go', believed to be a version of Psalms 122:1. An alternate version is 'DD M NOMINUS' or 'the gift of Marcus Nominus'. I couldn't access the Chapel and hence photos are only from the closed entrance. You can read this interesting link and learn how difficult it is to access the chapel.
St. James the Less on the other hand is identified as either the apostle James, the son of Alphaeus (Mark 15:40) or the 'brother of the Lord, (Acts 9:27; Gal 1:19), the first bishop of Jerusalem. He is also known as 'St. James the Just'.
Although the present Cathedral is from 12th-13th century, it was built over an earlier 6th century Byzantine Church. Despite being one of the most beautiful cathedrals in Jerusalem, St. James is not generally open to tourists outside the Armenian community. You can visit the cathedral only when the prayers are held and during the service it is advised to behave more like a worshiper than a tourist. Photography is also not promoted and many of the interesting sites are not accessible. Most of the photographs below were taken immediately after the service finished and before the cathedral was closed to public. I had to really rush and click these photos before the cathedral was closed after the prayers.