An atrium completely covered by a roof was extremely rare. With few exceptions, there was a large rectangular opening over the middle, _compluvium_, toward which the roof sloped from all sides (Figs. 114, 118). In the floor, directly under the compluvium, was a shallow basin, _impluvium_, into which the rain water fell (_h_ in Fig. 118). The impluvium had two outlets. One was connected with the cistern; a round cistern mouth, _puteal_, ornamented with carving, often stood near the edge of the basin, as in the house of the Tragic Poet (Fig. 153). The other outlet led under the floor to the street in front, carrying off the overflow when the cistern was full, and also the water used in cleaning the floor. In the better houses a fountain was often placed in the middle of the impluvium. Vitruvius (VI. iii. 1 _et seq._) mentions five kinds of atriums, the basis of classification being the construction of the roof--Tuscan, tetrastyle, Corinthian, displuviate, and tortoise atriums. The first three are well illustrated at Pompeii. The Tuscan atrium, supposed by the Romans to have been derived from the Etruscans, was apparently the native Italic form. Two heavy girders were placed across the room, above the ends of the impluvium (Fig. 117, _b_). On these, two shorter crossbeams were laid (_c_), over the sides of the impluvium. The corners of the rectangular frame thus made were connected with the walls at the corners of the atrium by four strong slanting beams (Figs. 117, 118, _e_). On these and on the frame were placed the lower ends of the sloping rafters (Fig. 117, _f_), carrying the tiles, the arrangement of which can be seen in Figs. 114, 117, and 118. This was the most common arrangement of the roof at Pompeii. [Illustration: Fig. 117.--A Tuscan atrium: plan of the roof. _a_, _a._ Side walls. _b._ One of the two girders supporting the roof. _c._ Crossbeam, resting on the two girders. _d._ Short beam of the thickness of _c_. _e._ Corner beam. _f._ Rafters, sloping toward the inside. _g._ Compluvium. 1. Flat tiles, _tegulae_. 2. Semicylindrical tiles for covering the joints, _imbrices_. 3. Gutter tiles.] The edge of the compluvium was frequently ornamented with terra cotta waterspouts, representing the heads of animals. In a house near the Porta Marina the projecting foreparts of dogs and lions were used in place of the heads; the remains of a part of the compluvium have been put together again, and are seen in Fig. 119. The lions were placed over the larger spouts at the four corners; the under side of the spouts surmounted by the dogs and lions was ornamented with acanthus leaves in relief. The same illustration presents an example of the antefixes sometimes found.