The remainder of these studies show two different systems; in the
first the dome rises from a square plan,--in the second from an
octagonal base._

_Group III.

Domes rising from a square base and four pillars. [Footnote 1: The
ancient chapel San Satiro, via del Falcone, Milan, is a specimen of
this type.]_

a) First type. _A Dome resting on four pillars in the centre of a
square edifice, with an apse in the middle, of each of the four
sides. We have eleven variations of this type.

aa) Pl. LXXXVIII, No. 3.

bb) Pl. LXXX, No. 5.

cc) Pl. LXXXV, Nos. 2, 3, 5.

dd) Pl. LXXXIV, No. 1 and 4 beneath.

ee) Pl. LXXXV, Nos. 1, 7, 10, 11._

b) Second type. _This consists in adding aisles to the whole plan of
the first type; columns are placed between the apses and the aisles;
the plan thus obtained is very nearly identical with that of S.
Lorenzo at Milan.