Comparing these scales with the Species of the Octave, we find a certain amount of correspondence. As has been already noticed (p. 22), the names Syntono-lydian and Lydian answer to the ordinary Lydian and Hypo-lydian respectively. Accordingly the Lydian of Aristides agrees with the Hypo-lydian species as given in the pseudo-Euclidean _Introductio_. The Dorian of Aristides is the Dorian species of the _Introductio_, but with an additional note, a tone below the Hypatê. The Phrygian of Aristides is not the Enharmonic Phrygian species; but it is derived from the diatonic Phrygian octave _d-e-f-g-a-b-c-d_ by inserting the enharmonic notes _e*_ and _b*_, and omitting the diatonic _g_. By a similar process the Mixo-lydian of Aristides may be derived from the diatonic octave _b-b_, except that _a_ as well as _g_ is omitted, and on the other hand _d_ is retained. If the scale of the Syntono-lydian is completed by the lower _c_ (as analogy would require), it will answer similarly to the Lydian species (_c-c_). § 34. _Credibility of Aristides Quintilianus._ But what weight can be given to Aristides as an authority on the music of the time of Plato? The answer to this question depends upon several considerations. 1. The date of Aristides is unknown. He is certainly later than Cicero, since he quotes the _De Republica_ (p. 70 Meib.). From the circumstance that he makes no reference to the musical innovations of Ptolemy it has been supposed that he was earlier than that writer. But, as Aristides usually confines himself to the theory of Aristoxenus and his school, the argument from silence is not of much value. On the other hand he gives a scheme of notation containing two characters, [Symbol: [] and [Symbol: *], which extend the scale two successive semi-tones beyond the lowest point of the notation given by Alypius[1]. For this reason it is probable that Aristides is one of the latest of the writers on ancient music. [Footnote 1: This argument is used, along with some others not so cogent, in Mr. W. Chappell's _History of Music_ (p. 130).] 2. The manner in which Aristides introduces his information about the Platonic Modes is highly suspicious. He has been describing the various divisions of the tetrachord according to the theory of Aristoxenus, and adds that there were anciently other divisions in use. So far Aristides is doubtless right, since Aristoxenus himself says that the divisions of the tetrachord are theoretically infinite in number (p. 26 Meib.),--that it is possible, for example, to combine the Parhypatê of the Soft Chromatic with the Lichanos of the Diatonic (p. 52 Meib.). But all this concerns the genus of the scale, and has nothing to do with the species of the Octave, with which Aristides proceeds to connect it. It follows either that there is some confusion in the text, or that Aristides was compiling from sources which he did not understand.