Fig. 29 exhibits on one side the head of Pallas, and on the reverse a little square labyrinth placed beside an owl standing upon a prostrate amphora. In Fig. 30 the obverse is occupied by the head of Apollo, the reverse by a labyrinth of circular shape, but conforming to the conventional plan. The head on the coin shown in Fig. 31 may be intended for that of Minos or Zeus. On the reverse is a square labyrinth. Labyrinthine designs are also found on certain Lydian, Phrygian, and Ionian coins. It will be noticed that when once the labyrinth pattern has been definitely conventionalised it remains very constant in principle, whether its general conformation be rectangular or circular. Starting from the exterior, the "path" runs inwards a short distance, turns so as to run parallel with the outer wall until nearly a full circuit has been completed, then doubles back on itself and runs round in the opposite direction, doubles upon itself again, and so on until it finally comes to a stop in a blind end, having traversed all of the space within the outer walls without covering any part twice and without forming any branches or loops. Obviously there is no "puzzle" about this kind of labyrinth; one has simply to follow the one path, either to penetrate to the inner goal or to escape thence to the exterior. A labyrinth of precisely this type was discovered traced on the surface of a crimson-painted pillar in the peristyle of the building known as the House of Lucretius, in the excavated portion of Pompeii (Fig. 32). It was evidently scratched with a nail or stylus by some idler of 2000 years ago (Pompeii was overwhelmed by Vesuvius in A.D. 79) and is accompanied by the words "LABYRINTHUS. HIC HABITAT MINOTAURUS," possibly in waggish reference to the owner or occupier of the premises. [Illustration: FIG. 32.--_Graffito_ at Pompeii. (Museo Borbonico.)] Another house has, in consequence of its mosaic and pictorial references to the Cretan Labyrinth, received the name of the Casa del Labirinto or House of the Labyrinth. One mosaic discovered therein depicts Theseus and the Minotaur struggling on the ground, watched by a group of affrighted maidens. [Illustration: Figs. 26 to 31. Coins of Knossos. (British Museum)]