MS. B. 19. A further development of MS. B. 18, by employing for the
four principal chapels the type Pl. LXXXVIII No. 3, as we have
already seen in Pl. XCI No. 2; the exterior presents two varieties.

a) The outer contour follows the inner. [Footnote 2: These chapels
are here sketched in two different sizes; it is the smaller type
which is thus formed.]

b) It is semicircular.

Pl. LXXXVII No. 2 (MS. B. 18b) Elevation to the first variation MS.
B. 19. If we were not certain that this sketch was by Leonardo, we
might feel tempted to take it as a study by Bramante for St. Peter's
at Rome. [Footnote 3: See_ Les projets primitifs Pl. 43._]_

_MS. P. V. 39b. In the principal axes the chapels of MS. B. 19, and
semicircular niches on the diagonals. The exterior of the whole
edifice is also an octagon, concealing the form of the interior
chapels, but with its angles on their axes.

Group V.

Suggested by San Lorenzo at Milan.

In MS. C. A. 266 IIb, 8l2b there is a plan almost identical with
that of San Lorenzo. The diagonal sides of the irregular octagon are
not indicated.

If it could be proved that the arches which, in the actual church,