2 Teucrigenas alludes to the legend of Britain’s Trojan settlement. As for the word itself, Cheek (p. 117) compares Troigenas at Vergil, Aeneid I.19 and VIII.117.
6 For occultique doli cf. Tibullus I.ix.24.
8 Carey-Fowler noted that Vergil calls Pluto father of the Furies at Aeneid VII.327 and Saturn an exsul Olympo at VIII.319f. Cheek wrote (p. 181) that “the lines which bring [Summanus] first into the poem introduce him as the regnans Acheronte tyrannus and, in almost immediate juxtaposition, as the aethereo vagus exul Olympo thus establish him from the beginning in that dual role of ’Hell’s dread emperor’ (Paradise Lost II.510) and ‘Heav’ns fugitive’ (P. L. II.57), an idea in paradox, which, though not further developed here, is at the root of all his Paradise Lost soliloquies, and a major motivation behind much of his action there. And here, as there, it makes of him the restless wanderer.”
9 Cf. errat per orbem at Ps. - Seneca, Hercules Oetaeus 417. Cheek goes on to compare this line with Paradise Regained I.33f. (of Satan), who roving still / About the world…
10 For sceleris socios cf. Campion’s de Coniuratione Pulverea I.382 Carey-Fowler pointed out that vernales indicates slaves by birth, and compared Milton’s remarks on predestination at De Doctrina I.iv (XIV.129f. of the Columbia edition). Cheek (loc. cit.) compared Paradise Lost I.571, Their number last he sums, and PL I.606, The fellows of his crime, the followers rather.
15 Warton noted that the adjective olivifer is found at Ovid, Fasti III.151 and Ibis 317.
16 Cheek (p. 182) compared Paradise Lost IV.110f., by thee at least / Divided Empire with Heav’ns King I hold.
17 Cheek also compared Paradise Lost IV.121, Artifcer of fraud.
20 For the Caspian tigress (no doubt a close cousin to the Hyrcanian one) cf. Statius, Thebais X.288f.
21 Cheek (p. 177) compared Vergil, Aeneid I.21, populum late regem . 
22ff. Cheek (p. 178) compared the simile of a night-ranging wolf at Aen. IX.59ff.
23 The antecedent of talibus is less than wholly self-evident. Summanus was an obscure and probably ancient Roman god of nocturnal lightning. For his obscurity, cf. Ovid, Fasti VI.731, reddita, quisquis is est, Summano templa feruntur. His nature is described by Pliny, Natural History II.cxxxviii, Tuscorum litterae novem deos emittere fulmina existimant, eaque esse undecim generum; Iovem enim trina iaculari. Romani duo tantum ex iis servavere, diurna attribuentes Iovi, nocturna Summano, rariora sane eadem de causa frigidioris caeli. Pliny also mentions the temple of Summanus at XXIX.lvii. In his note on this line, Merritt Y. Hughes noted that this information was readily available to Milton and his readers thanks to an entry in Carolus Stephanus’ Dictionarium Historicum, Geographicum, Poeticum printed at Geneva in 1621.
24 Was the nickname Old Blue Fire given to Stonewall Jackson by a literate trooper who remembered this line? Cf. Vergil, Aeneid III.573, turbine fumantem piceo.
25 Note the pun on Albion in albentia…arva.
26f. Carey-Fowler glossed these lines with a passage from Milton’s History of Britain (X.4 of the Columbia edition ): in which Milton told the legend of the giant Albion, son of Neptune, who reigned in England “44 years. Till at length passing over into Gaul, in aid of his brother Lestyrgon, against whom Hercules was hasting out of Spain itno Italy, he was slain in fight.”
31 Cf. Ovid, Metamorphoses II.794f. (from a passage in which Envy catches sight of Athens). It is apposite to quote the entire passage, II.787ff.):

illa deam obliquo fugientem lumine cernens
murmura parva dedit successurumque Minervae
indoluit baculumque capit, quod spinea totum
vincula cingebant, adopertaque nubibus atris,
quacumque ingreditur, florentia proterit arva
exuritque herbas et summa cacumina carpit
adflatuque suo populos urbesque domosque
polluit et tandem Tritonida conspicit arcem
ingeniis opibusque et festa pace virentem
vixque tenet lacrimas, quia nil lacrimabile cernit.

32 Cf. Aeneid XI.122, Cerealia dona rigebant.
35 Carey-Fowler noted the echo of Aeneid. XIV.791, lurida…sulphura. 
38 Carey-Fowler compared Paradise Lost I.193f.:

With head uplift above the wave, and
Eyes that sparkling blazed.

Cf. also Statius, Thebais VI.790, dentibus horrendum stridens.
39 For armorum fragor cf. Lucan I.569. For cuspide cuspis cf. Statius, Thebais VIII.399 (also at line-end).
41 For gens…rebellis cf. Alabaster’s Elisaeis 243.
42 For potentior arte cf. Ovid, Metamorphoses XI.494.
48 Carey-Fowler remarked the imitation of Lucan I.183, iam gelidas Caesar cursu superaverat Alpes.
49 For Ausonia fines cf. Vergil, Aeneid VI.345, Ovid, Tristia I.ii.92 and I.iii.6.
50 For priscique Sabini cf. Ovid, Fasti II.477 and Martial X.xxxiii.1 (and also, perhaps, Vergil, Aeneid VII.706, Sabinorum prisco de sanguine).
51 Milton may have been thinking of Hesiod, Theogony 1016, in which it is stated that the sons of the witch Circe migrated to Etruria; numerous ancient passages speak of the Etruscans’ prowess at medicine and the concoction of philtres. 
52 I. e., the Tiber runs gently to the sea. For this use of Thetis, Carey-Fowler cited Vergil, Eclogue iv.32.
53 Quirinus was the name of the deified Romulus. Carey-Fowler compare Martigenam…Quirinum at Ovid, Fasti I.199.
54 They also noted the echo of Ovid, Metamorphoses XI.596, dubiaeque crepuscula lucis.
56 The gods made of bread are of course the Host. Milton’s Puritanism is already visible here.
57 For summisso poplite cf. Catullus lxiv.370.
58 Cheek (p. 178) compared Vergil, Aeneid I.67, gens inimica mihi.
60f. For the Cimmerians who dwell in perpetual darkness cf. Odyssey xi.13ff. Cf. the similar picture of the interior of St. Peter’s at William Alabaster’s Elisaeis 203ff.:

intus splendor iners atque horror opacus adumbrat
nec luci permissus honor, sed cerea flamma
palpitat, et crassis partitur regna tenebris.

62 The feast of St. Peter is on June 28.
64ff. Bromius is a cult title of Dionysus. Milton compares the music of St. Peter’s to the yowling of a bacchantes’ orgy on the mountains, as described by Euripides in The Bacchae. Cheek (p. 178) compared the similar Vergilian similes at Aen. IV.300ff. and VII.385ff.
65ff. “Echion, one of the heroes who sprang from the dragon’s teeth sown by Cadmus, founded the citadel of Thebes: thus Echionius may mean Theban, or since Thebes was chief city of Boeotia, Boeotian. Aracynthus: a mountain between Boeotia and Attica. Asopus: a river in Boeotia flowing near Mount Cithaeron, which is mentioned as the scene of Bacchic orgies by Ovid, Met. iii.702 and Vergil, Aen. iv.303”: Carey-Fowler.
66 For vitreis…undis cf. Vergil, Aeneid VII.759, Ovid, Metamorphoses V.48, Martial, Epigrams VI.lxviii.7, and Statius, Silvae III.ii.17.
69 According to Hesiod, Night was the sister of Erebus and by him gave birth to Aether and Day (Theogony 123ff.).
71ff. Vergil mentons the chariot of Night at Aeneid V.721 (cf. also, perhaps, the Vergilian Culex 202, iam quatit et biiuges oriens Erebeis equos nox), and, as Carey-Fowler noted, Spenser describes the “cole blacke steedes” that draw it at Faerie Queene I.v.20. Milton names and describes the horses; their names are derived from the Greek words typhlos (“blind”), melan (“black”) + chaite (“tress of hair”), siope (“silence”), and phrix (“shuddering”). Tresses of hair were cut off at Greek funerals.
78 Pluto is called umbrarum dominus at Ovid, Metamorphoses X.16.
80ff. Carey-Fowler pointed out that details of this description are taken from from George Buchanan’s Franciscanus, in which St. Francis is described as cannabe cinctus and has obrasum…caput duro velante cucullo (19f.). Likewise Buchannan describes a friar as having longo sub syrmate rasum…caput (45ff.), and in his Somnium 5ff. (printed among the Fratres Fraterrimi) the friar who appears to the poet wears a fenestratus calceus. In his note on these lines Warton quoted an anonymous correspondent’s explanation that “The fenestrati calcei are the sandals, or soles, tied on the foot by straps, or thongs of leather, crossed, or lattice-wise, which are usually worn by the Franciscan friars.” In the Introduction I have suggested that Milton’s inspiration for this disguise was the nameless hooded devil who appears at Campion’s de Pulverea Coniuratione I.75ff. Carey-Fowler draw an unconvincing comparison with the disguised Satan at Paradise Regained I.314ff. and 497f.: there is no compelling reason for regarding this latter individual as a religious figure of any sort, rather than a simple old rustic fellow.
89 St. Francis was supposed to have tamed the wolf of Gubbio (cf. the Fioretti xxi), but I do not recall any similar tale involving a Libyan lion.
90 For velatus amictu cf. Ovid, Fasti III.363 and Metamorphoses X.1 (both at line-end).
92 Cheek (p. 178) compared Vergil, Aeneid IV.560, nate dea, potes hoc sub casu ducere somnos?
93 Cheek also compared Aen. IV.267, heu regni rerumque oblite tuarum?
95 For Hyperboreo…axe cf. Juvenal vi.570 and Statius, Thebais XII.650.
96 The British are called pharetrati because the longbow was the characteristic English weapon.
97 For surge, age cf. Vergil, Aeneid III.169, VIII.59, X.241, Ovid, Ars Amatoria I.548, Heroides xiv.73, and Metamorphoses I.548. This is said to dreaming Aeneis by his penates at Aen. III.169. Cf. Ovid, Metamorphoses I.26.
102 Cf. Vergil, Aeneid I.128, disiectam Aeneae toto videt aequore classem. The allusion is of course to the Armada: for Hesperia as Spain, cf. Campion’s use of Hesperii for the Spanish at ad Thamesin 60, 96, 134, 214, and de Pulverea Coniuratione I.249. This usage is also found at also Charles Fitzgeoffrey, Affaniae (1601) III.57.2 and Cenotaphia (1601) 9.2): Fitzgeoffrey’s Affaniae is in many respects very much modeled on Campion’s 1595 Thomae Campiani Poemata.
103 For lato…profundo cf. Statius, Thebais V.283.
105 Perhaps following the example of William Alabaster, Elisaeis 539ff., Milton compares Queen Elizabeth to Hippolyte or similar Amazon warrior.
109 For signaque…fulgentia cf. Ovid, Metamorphoses XIII.700 and Lucan, Bellum Civile II.576.
111 A reversal of the situation described by Alabaster, Elisaeis 215 and 283, in which the Pope tramples kings underfoot.
112 Cf. Lucan X.346, detecto Marte lacessit (also at line-end).
114 Cheek (p. 183) compared Paradise Lost I.645ff.:

our better part remains
To work in close, by fraud our guile
What force effected not.

For irritus…labor cf. Seneca, Agamemnon 16f.
116 Consilium can be used to designate a deliberative body, so the printed text can stand. Nevertheless, in view of the phonetically-drive confusion of seu for ceu in line 20, one wonders if Milton wrote concilium. For extremis…oris cf. Lucretius V.583, Vergil, Georgics II.171, Ovid, Metamorphoses VIII.788, Propertius II.x.17, and Lucan, Bellum Civile IV.1.
124 For iussa facessere cf. the Commentary note on Herring’s Pontificia Pietas 59f.
125 In his relentless search for Vergilian parallels Cheek (p. 178) compared such descriptions of fearful astonishment at those at Aeneid I.93, III.30, and VI.559.
129 For divos divasque as a designation for the Saints; in the same way, Thomas Campion called the saits numina at de Pulverea Coniuratione I.574.
132 Cheek (p. 178) compared Vergil, Aeneid II.4, lamentabile regnum.
133f. Dawn was wife of Tithon and mother of the hero Memnon; after his death she wept in mourning (Robert Graves, The Greek Myths § 164; the story is told at Ovid, Metamorphoses XIII.576ff.). Cheek (p. 179) compared Vergil, Aeneid IV.584f.: 

et iam prima novo spargebat lumine terras
Tithoni croceum linquens Aurora cubile.

134 Cf. lumine vestit at Vergil, Aeneid VI.640.
136 For montana cacumina cf. Ovid, Metamorphoses I.310.
139 For caligine noctis cf. Lucretius IV.456.
142 Cf. Lucan, Bellum Civilie VI.780, effera Romanos agitat discordia manes.
148 Carey-Fowler compare Horror flying about in Mammon’s cave at Spenser’s Faerie Queene II.vii.23.
149 For per muta silentia cf. Ovid, Metamorphoses VII.184.
153 Although this picture is different, the verbal components from which it is made come from Vergil, Aeneid I.165f.:

horrentique atrum nemus imminet umbra.
fronte sub adversa scopulis pendentibus antrum.

154 Cf. Seneca, Agamemnon 714f. (from a description of panic): 

incerta nutant lumina et versi retro
torquentur oculi.

158f. Carey-Fowler noted the echo of Horace, Odes I.iii.21ff.:

nequiquam deus abscidit
prudens oceano dissociabili
terras, si tamen inpiae
non tangenda rates transiliunt vada.

This seems like a deliberate inversion of the common contemporary topos (found at William Alabaster’s Elisaeis 30) that some friendly god made England an isolated island to guard it against the outside world: here nature made it such to protect the outside world from England.
161 Cf. celsior ille per auras / difflatur at the Vergilian de Rosis Nascentibus 20f.
164 Cf. Vergil,Aeneid V.712, hunc cape consiliis socium.
166ff. Milton includes this crucial event, in which God catches sight of the Plot, which is also found in the works of his predecessors: cf. Wallace, in Serenissimi Regis Iacobi 306ff., Herring, Pontificia Pietas 267ff., and Phineas Fletcher, Locustae 699ff. (the equivalent plot development at Campion’s de Pulverea Coniuratione I.627ff. is somewhat different). Cf. longum curvamine caelum at Ovid, Metamorphoses VI.64 (also echoed by Campion at ad Thamesin 132).
168 Cf. Alabaster, Elisaeis 45, et coniuratas vano conamine turmas..
169 The future force of the book’s volet is far from clear. God now wishes to aid the English and so gives His mandate to Fame (201 - 3). Volet might make sense according to the assumption Milton is here looking past this first divine intervention and anticipating God’s second act of intervention described at 220f., but this seems a somewhat unnatural interpretation and the strong suspicion arises that the typesetter has misread his handwriting and that he in fact wrote vult. Then too, one would expect a verb coordinated in tense with the present ones in the preceding two lines. Alternatively, Prof. Karl Maurer suggests to me, “ I do agree that the future looks queer; but I myself dislike not only the tense but even the verb; to me vult seems a bit vapid, coming as it does after two more colorful verbs, fulgurat...ride.t I wonder if volet is not from volo = “fly?” Perhaps [Milton] wrote volat and meant “and who flies to protect &c.,” i. e., intueri, inf. of purpose with a verb of motion (or = complementary inf.: “who hastens to protect.”)
171 The printed text of both editions has Mareotidas, referring to an Egyptian lake in the vicinity of Alexandria. Dewitt T. Starnes emended the reading to Maeotidas at Notes and Queries 96 (1951) 515ff. For Lake Maeotis (the Sea of Azov) as the boundary between Europe and Asia, Starnes he cited Lucan III.272ff.. See, however Alan H. Gilbert, “The Tower of Fame in Milton,” Modern Language Notes, vol. xxviii, no. 1 (Jan. 1913), pp. 30f. and D. Bush in A Variorum Commentary on the Poems of John Milton (London, 1970) I.193, n. 171. Prof. Karl Maurer also reminds me that the Romans sometimes regarded the Nile as the boundary between Europe and Africa, citing Vergil, Georgics II.287 - 290.
spacerThis passage is heavily indebted to Ovid’s description of the house of Fame at Metamorphoses XII.39ff., which is also located at the center of the world:

orbe locus medio est inter terrasque fretumque
caelestesque plagas, triplicis confinia mundi;
unde quod est usquam, quamvis regionibus absit,
inspicitur, penetratque cavas vox omnis ad aures:7
Fama tenet summaque domum sibi legit in arce,
innumerosque aditus ac mille foramina tectis
addidit et nullis inclusit limina portis;
nocte dieque patet: tota est ex aere sonanti,
tota fremit vocesque refert iteratque quod audit;
nulla quies intus nullaque silentia parte,
nec tamen est clamor, sed parvae murmura vocis,
qualia de pelagi, siquis procul audiat, undis
atria turba tenet: veniunt, leve vulgus, euntque
mixtaque cum veris passim commenta vagantur
milia rumorum confusaque verba volutant;
e quibus hi vacuas inplent sermonibus aures,
hi narrata ferunt alio, mensuraque ficti
crescit, et auditis aliquid novus adicit auctor.
illic Credulitas, illic temerarius Error
vanaque Laetitia est consternatique Timores
Seditioque repens dubioque auctore Susurri;
ipsa, quid in caelo rerum pelagoque geratur
et tellure, videt totumque inquirit in orbem.

174 Athos, Pelion, and Ossa are three Greek mountains. The Giants piled Pelion atop Ossa in their attempt to storm Olympus.
178 Carey-Fowler compared Homer’s similes of flies swarming at a milk pail at Iliad II.469ff. and XVI.641ff.
181ff. Milton is also indebted to Vergil’s description of Rumor at Aeneid IV.180ff.:

progenuit pedibus celerem et pernicibus alis,
monstrum horrendum, ingens, cui quot sunt corpore plumae,
tot vigiles oculi subter (mirabile dictu),
tot linguae, totidem ora sonant, tot subrigit auris.
nocte volat caeli medio terraeque per umbram
stridens, nec dulci declinat lumina somno;
luce sedet custos aut summi culmine tecti
turribus aut altis, et magnas territat urbes,
tam ficti pravique tenax quam nuntia veri.

184 For patuli…orbis cf. Horace, Ars Poetica 132 and Lucan, Bellum Civile IX.502.
185 In mythology Argus (who guarded Io, the iuvenca Isidos) was the son of Arestor, and so one would expect Arestoride here, not the book’s Aristoride. While writing these lines Milton was surely thinking of Ovid, Metamorphoses I.624ff.:

donec Arestoridae servandam tradidit Argo.
centum luminibus cinctum caput Argus habebat
inde suis vicibus capiebant bina quietem,
cetera servabant atque in statione manebant.
constiterat quocumque modo, spectabat ad Io,
ante oculos Io, quamvis aversus, habebat.

188 For lumina…spectantia cf. Ovid, Metamorphoses VI.66 and Tristia IV.iii.43f.
189f. The Columbia edition translator has With these eyes Rumor is wont, often, to traverse places that lack the light… Istis more likely refers to Rumor’s myriad ears, which in the preceding epic simile are compared to Argus’ eyes in number and, by implication, tirelessness and information-gathering capacity. With these ears she can find out what is occurring even in the darkest places, which she certainly could not do with her eyes (and in this sense she is superior to Argus). Cf., perhaps, the phrase luce carentia regna used for the Underworld by Ovid, Metamorphoses XV.532.
195 Cf. Vergil, Aeneid IV.174, Fama, malum qua non aliud velocius ullum. Milton relies on the individual reader to recall the specific operation by which Rumor rescues the British, the mysterious letter sent to Lord Monteagle.
196 Cf. Aen. IV.335, nec me meminisse pigebit.
202 Cf. coniuratas…turmas at Alabaster, Elisaeis 45 (a line already laid under contribution at 168).
205 For stridentes…alas cf. Vergil, Aeneid VII.561 and the Vergilian Ciris 515.
206 For variis…plumis cf. Horace, Ars Poetica 2.
207 Carey-Fowler observed that Temese in sourthern Italy was the site of a famous copper mine mentioned by Homer at Odyssey I.184. Cf. Temesaea…ora at Ovid, Fasti V.441 and Metamorphoses 207f.
208 Cf., perhaps, remigii…pennarum at Lucretius VI.743.
209 Cf. Vergil, Aeneid VII.807, cursuque pedum praevertere ventos.
212 Cf. Aen. II.98f. spargere voces…ambiguas.
215 Printed texts have Authoresque addidit, but in a private letter Ludwig Bernays pointed to me that Addidit authores is metrically superior, and I orginally adopted this reading. So too Philip Hardie, (Cambridge, 2012), p. 432. But Prof. Karl Maurer has more recently reminded me that the 1645 Poems of Mr. John Milton, both English and Latin, and, A maske of the same author has an even better authoresque addit, followed by the Rev. H. C. Beeching M. A., Poetical Works of John Milton (Oxford, 1900).
218 Effaetique senes was suggested by effeta senectus at Vergil, Aeneid VII.440, VII.452, and VIII.508.
221 For crudelibus obstitit ausis cf. Ovid, Heroides xiv.49.
223 Cf., perhaps, pia tura soluta at Juvenal xiii.116. And cf. also Phineas Fletcher, Locustae 594f. (evidently the only verbal resemblance between these poems and so possibly coincidental):

ipse tibi vota, et pia thura frequenter
imponam, et summos iam nunc meditabor honores.

225 Cf. choros with forms of agito at Vergil, Georgics IV.533 and Seneca, Hercules Furens 879.