It is evident that the principle followed in the formation of these galleries and _loculi_ was the securing of the greatest amount of space for graves with the least excavation. Hence the passages are made as narrow as possible. The graves are also as close together as the friable nature of the _tufa_ will permit, and are made to suit the shape of the body, narrow at the feet, broader at the shoulders, and often with a semi-circular excavation for the head, so as to avoid any superfluous removal of _tufa_. Sometimes the _loculi_ were made large enough to hold two, three, or even four bodies, which were often placed with the head of one toward the feet of the other, in order to 20 economize space. These were called _bisomi_, _trisomi_, and _quadrisomi_, respectively. The graves were apparently made as required, probably with the corpse lying beside them, as some unexcavated spaces have been observed traced in outline with chalk or paint upon the walls. Almost every inch of available space is occupied, and sometimes, though rarely, graves are dug in the floor. 21 The _loculi_ are of all sizes, from that of the infant of an hour to that of an adult man. But here, as in every place of burial, the vast preponderance of children’s graves is striking. How many blighted buds there are for every full-blown flower or ripened fruit! Sometimes the _loculi_ were excavated with mathematical precision. An example occurs in the Cemetery of St. Cyriaca, where at one end of a gallery is a tier of eight small graves for infants, then eight, somewhat larger, for children from about seven to twelve, then seven more, apparently for adult females, and lastly, a tier of six for full-grown men, occupying the entire height of the wall. Generally, however, a less regular arrangement was observed, and the graves of the young and old were intermixed, without any definite order.