Light will be thrown on this obscure subject by an inquiry into the relation of the sources to one another. It seems certain that Fabius derived his information concerning the tribes and the entire centuriate organization from the “discriptio centuriarum”—a document in the censors’ office. Though ascribed to Servius Tullius as author,[285] it set forth the centuriate system as it existed in reality before the reform—that is in the time of the first war with Carthage.[286] It was this late form of the centuriate organization which Fabius had in mind. He must have been prevented, however, from ascribing to Servius the institution of all the thirty-three tribes then existing, by the recollection that two tribes were added as recently as 299 from territory too far from Rome to have formed a part of her domain under Servius; and perhaps the curiate organization led him to favor the number thirty. He made Servius the author of thirty tribes, accordingly, in spite of the fact that this number was not reached till 318. His error is not more absurd than the ascription to Servius of the whole centuriate organization as it stood at the opening of the First Punic War, or the assumption that in the first Servian census were enrolled eighty thousand men fit for military service.[287] Cato, who also states the original number as thirty, without separating them into rural and urban,[288] may have been influenced by Fabius, though it is likely that he drew from the same source. Vennonius in making Servius the author of all thirty-five tribes but slightly exceeds the absurdity of earlier writers.[289] Evidently Fabius and Cato were the sources for all future annalists. While depending on them, Varro seems to have noticed the error of ascribing twenty-six rural tribes to Servius, as there were but seventeen of this class before 387. To avoid the difficulty and at the same time to retain the Fabian number, he supposed that the country districts of Servius were not yet tribes but the regiones from which the tribes were afterward formed[290]—a superficial explanation in the true Varronian style.[291] Following Varro, however, later authorities generally speak of the four urban tribes of Servius without mentioning those of the country.[292] So Dionysius, after referring to the four city tribes, proceeds to describe their character and functions, as though these were all the tribes then existing.[293] Thus far he depends upon Varro. Fortunately, however, he gained from Fabius the information that there were also twenty-six rural tribes, his description of which[294] is slightly troubled by the Varronian notion that these country districts were not so much tribes as regiones, πάγοι, but which served all the purposes of tribes including the taking of the census.[295]