The aedes Volcani in circo Flaminio was dedicated before 215 B.C.; the exact date is not known[904]. Its position was explained by Vitruvius[905] as having the object of keeping conflagrations away from the city. Mr. Jevons, in his Introduction to a translation of Plutarch’s _Quaestiones Romanae_[906], has argued from this position, outside the pomoerium, and from a doubtful etymology, that the cult of Volcanus was a foreign introduction; but the position of the temple is no argument, as has been well shown by Aust[907], and the chief area Volcani, or Volcanal, was in the Comitium, in the heart of the city[908]. IX KAL. SEPT. (AUG. 24). MUNDUS PATET. This does not appear in the calendars. We learn from Festus[909] that on this day, on Oct. 5, and Nov. 8, the ‘mundus’ was open. This mundus was a round pit on the Palatine, the centre of Roma quadrata[910]—the concave hollow being perhaps supposed to correspond to the concave sky above[911]. It was closed, so it was popularly believed, by a ‘lapis manalis’ (Festus s. v.). When this was removed, on the three days there was supposed to be free egress for the denizens of the underworld[912]. I am much inclined to see in this last idea a later Graeco-Etruscan accretion upon a very simple original fact. O. Müller long ago suggested this—pointing out that in Plutarch’s description of the foundation of Roma quadrata the casting into the trench of first-fruits of all necessaries of life gives us a clue to the original meaning of the mundus. If we suppose that it was the _penus_ of the new city—a sacred place, of course—used for storing grain, we can see why it should be open on Aug. 24[913]. Nor is it difficult to understand why, when the original use and meaning had vanished, the Graeco-Etruscan doctrine of the underworld should be engrafted on this simple Roman stem. Dis and Proserpina claim the mundus: it is ‘ianua Orci,’ ‘faux Plutonis’[914]—ideas familiar to Romans who had come under the spell of Etruscan religious beliefs. VIII KAL. SEPT. (AUG. 25). NP. OPIC[ONSIVIA]. (ALLIF. MAFF. VALL.) OPICID. (PINC.) The last two letters must be a cutter’s error. FERIAE OPI; OPI CONSIV. IN REGIA. (ARV.) The last four words seem to belong to Aug. 26 (see Mommsen ad loc.).