The period of this jurist is determined by Capitolinus (Antonin. Piaus, 12), who states that Marcellus was one of the legal advisers of the emperor Antoninus Pius, and enumerates with him, Salvius Valens, Javolenus. and others. It also appears from his own writings that Marcellus lived under Pius, for he mentions a decision of Aurelius Antoninus (Dig. ,35. tit. 1. s. 48); if Aurelius Antonintis here means Pius, and itot Marcus his successor. That he was living under the Divi Fratres, Marcus Antoninus and L. Verus, appears from a reference which he makes to an oration of the two emperors respecting tutors giving security (satisdatio). The passage is a citation by Ulpian from Marcelltls, and the term Divi may be, and appears to be, the addition of Ulpian, and therefore does not prove that Marcellus survived Marcus Antoninus (Dig. 26. tit. 2. s. 19). Marcellus also quotes a judgment of Antoninus Augustus (Dig. 28. tit. 4. s. 3), by whom he means M. Antoninus, as appears from his naming the consuls Pudens and Pollio, who belong to A. D. 166. The question turned upon a will, in which the testator had cancelled the names of the heredes in his testament, and his property was claimed by the fiscus as bona caduca. The case was argued before the emperor by the advocati of the fiscus and the advocati of the claimants under the will. The emperor's judgment was in favour of the equitable interpretation, but against the strict law.

The conjecture that the Ulpius Marcellus, who commanded in Britain in the reign of Commodus, is the jurist, hardly needs refutation. The only ground for it is the sameness of name, to which it is objected that Dio Cassius, who speaks of the military talent of Ulpius Marcellus, says nothing of his legal reputation (Dio Cassius, 72.8, and the note of Reimarus). Besides this, it is very unlikely that a man who had been a jurist during the reigns of Pius and Marcus, the latter of which lasted near twenty years, should turn soldier under Commodus, the successor of Marcus, in the year A. D. 182. The soldier Marcellus may have been the son of the jurist.

The works of Marcellus mentioned in the Florentine Index are, thirty-one books of Digesta, six books on the Leges Julia et Papia, and a book of Responsa. But there are excerpts from other works of his in the Digest, as a work entitled " Publica" (Dig. 3. tit. 2. s. 22), the object of which may be collected from its being referred to under the title " De iis qui infamia notantur ;" on the office of a praesul (Dig. 4. tit. 4. s. 43); and on the office of a consul, the fifth book of which is quoted by Marcianus (Dig. 40. tit. 15. s. 1). Marcellus also commented on the writings of Salvius Julianus (Dig. 4. tit. 4. s. 11), and on Pomponius (Dig. 7. tit. 4. s. 29). Marcellus was commented on by Cervidius Scaevola (Dig. 24. tit. 1. s. 11) and Ulpian. He is often cited by subsequent jurists, especially Paulus and Ulpian, and by Modestinus, one of the latest of the jurists. There are 159 excerpts from Ulpius Marcellus in the Digest. This notice differs in some matters from that of Zimmern, Geschichte des Röm. Privatrechts, vol. ii. p. 358, whose authorities do not always agree with his text.