It is impossible to decide whether this Sicilian civilization ought to be included under the term megalithic.  If, as seems probable, the idea of megalithic building was brought to Europe by the immigration of a new race it is possible that a branch of this race entered Sicily.  In that case I should prefer to think that they came not at the beginning of the First Siculan Period as we know it, but rather earlier.  Certain vases found with neolithic burials in a cave at Villafrati and elsewhere in Sicily resemble the pottery usually found in megalithic tombs; one of them is in fact a bell-shaped cup, a form typical of megalithic pottery.  It is thus possible that an immigration of megalithic people into Sicily took place during the stone age, definitely later than the period of the earliest neolithic remains on the island, but earlier than that of such sites as the Castelluccio cemetery.  This, however, is and will perhaps remain a mere conjecture, though it is quite possible that there are in the interior of Sicily dolmens which have not yet come to the notice of the archaeologist; in this connection it is worth while to remember that up to five years ago the existence of dolmens in both Sardinia and Malta passed unnoticed.

If the inclusion of Sicily in the megalithic area is doubtful there is fortunately no question about the island of Sardinia.  Here we have one of the chief strongholds of the megalithic civilization, where the architecture displays its greatest variety and flexibility.  The simplest manifestation of megalithic building, the dolmen, was up till lately thought to be absent from Sardinia, but the researches of the last few years have brought to light several examples, of which the best known are those of Birori, where the chamber is approximately circular in plan.

The monuments, however, for which Sardinia is most famous are the nuraghi. A nuraghe is a tower-like structure of truncated conical form, built of large stones laid in comparatively regular courses (Pl.  II, Fig. 2).  The stones are often artificially squared, and set with a clay mortar.  The plan and arrangement of a simple nuraghe are usually as follows (Fig. 17):  The diameter of the building is generally under 30 feet.  A door of barely comfortable height even for an average man and surmounted by a single lintel-block gives access to a narrow passage cut through the thickness of the wall.  In this passage are, to the right, a small niche (c) just large enough to hold a man, and, on the left, a winding staircase in the wall (d) leading to an upper storey.  The passage itself leads into the chamber (a), which is circular, often with two or three side-niches (b b), and roofed by corbelling, i.e. by making each of the upper courses of stones in its wall project inwards over the last.  The upper chamber, which is rarely preserved, is similar in form to the lower.

[Illustration:  Plate II Fig. 1.  MNAIDRA, DOORWAY OF ROOM H]