It is true that the list of bishops given by Eusebius (H. E. iv. 5. 3) seems to have been unknown to Hegesippus, who says that Symeon, son of Clopas, the second bishop, lived to a great age and suffered martyrdom in the reign of Trajan (Eus. H. E. iii. 11, 32. 1). But in the Codex Marcianus there is a note which professes to be derived from the fifth book of the Hypotyposes of Clement, and gives the places of sepulture of certain apostles and apostolic men (the text will be found in Zahn, Forschungen, iii. 70). Here we read “Simon Cleophas, qui et Judas, post Jacobum episcopus, cxx annorum crucifixus est in Jerusalem Traiano mandante.” It seems clear that Clement had combined the statement of Hegesippus with another that made Judas bishop in Trajan’s time. Hence we may infer that the ἔγγραφα from which Eusebius drew his list of bishops were older than 200 A.D.
The other sign of borrowing from Hegesippus is the "Peter and Paul" reference at the beginning of the list. "Peter and Paul" is an artificiality developed to make Christianity imitate Roman cultural myths, in this case Romulus and Remus. Internal evidence suggests Hegesippus published his treatise on the 900th anniversary of Rome ("the tenth year of Antoninus").
Charles Bigg, A Critical and Exegetical Commentary on the Epistles of St. Peter and St. Jude (International Critical Commentary), published by T. & T. Clark (Edinburgh, 1901).
