DAMOISEAU.—­Consists of a complex arrangement of rings, an enclosure 23 miles in diameter, with a somewhat smaller enclosure placed excentrically within it (the N. side of both abutting on a bright plateau), with two large depressions intervening between their W. borders.  This peculiarity, almost unique, renders the formation an especially interesting object.  Damoiseau is situated on the W. side of Grimaldi, on the E. coast-line of the Oceanus Procellarum, from which the S.W. border rises at a gentle inclination.  On the N.W. there is a curious curved inflexion of the Mare, bounded by a bright cliff, representing probably the E. side of a destroyed ring, a supposition which is strengthened by the existence of a faint scar on the surface of the sea, extending in a curve from one extremity of the bay to the other, and thus indicating the position of the remainder of the ring.  A conspicuous little crater stands at the S. end of it, and two others some distance to the W. The smaller component of Damoiseau contains a low central ridge.

RICCIOLI.—­An immense enclosure, near the limb, N.E. of Grimaldi, bounded by a rampart which is very irregular both in form and height, though nowhere of great altitude, and much broken by narrow gaps.  It is especially low and attenuated on the N., where a number of ridges with intervening valleys traverse it.  On the S. also a wide valley cuts through it.  With the exception of a few low rounded hills and ridges, a short crater-row under the S.E. wall, and two small craters on the S.W., there are no details on the floor, which, however, is otherwise remarkable for the dusky tone of its surface, especially on the N. This dark patch occupies the whole of the N.E. side of the interior, and is bounded on the S. by an irregular outline, extending at one point nearly to the centre, and on the W. by a curved edge.  The W. side is much darker than the rest.  It is, in fact, as dark, if not darker, than any part of the floor of Grimaldi.  Riccioli extends 106 miles from N. to S., and is nearly as broad.  It includes an area of 9000 square miles.

ROCCA.—­An irregular formation, 60 miles in length, near the limb S.E. of Grimaldi, consisting of a depression partially enclosed by mountain arms.

SIRSALIS.—­The more westerly of a conspicuous pair of ring-plains about 20 miles in diameter, in the disturbed mountain region some distance S.W. of Grimaldi.  It has lofty bright walls, rising to a great height above a depressed floor, on which there is a prominent central mountain.  The E. border encroaches considerably on the somewhat larger companion, which is, however, scarcely a third so deep.  One of the longest clefts on the visible surface runs immediately W. of this formation.  Commencing at a minute crater on the N. of it, it grazes the foot of the W. glacis; then, passing a pair of small overlapping craters (resembling Sirsalis and its companion in miniature), it runs through a very rugged country to a ring-plain E. of De Vico (De Vico a), which it traverses, and, still following a southerly course, extends towards Byrgius, in the neighbourhood of which it is apparently lost at a ridge, though Schmidt and Gaudibert have traced it still farther in the same direction.  It is at least 300 miles in length, and varies much in width and character, consisting in places of distinct crater-rows.