ARZACHEL.—­Another magnificent object, associated on the N. with Alphonsus, about 66 miles in diameter, and encircled by a massive complex rampart, rising at one point more than 13,000 feet above a depressed floor.  It presents some very suggestive examples of terraces and large depressions, the latter especially well seen on the S.E.  The bright interior includes a large central mountain with a digitated base on the S.E., some smaller hills on the S. of it, a deep crater W. of it (with small craters N. and S.), and, between the crater and the foot of the W. wall, a very curious winding cleft.

LASSELL.—­This ring-plain, some 14 miles in diameter, is irregular both as regards its outline and the width of its rampart.  There is a crater on the crest of the N.W. wall, just above a notable break in its continuity through which a ridge from the N.W. passes.  There is another crater on the opposite side.  The central mountain is small and difficult to see.  About 20 miles N.E. of Lassell is a remarkable mountain group associated with a bright crater, and further on in the same direction is a light oval area, about 10 miles across, with a crater (Alpetragius d) on its S. edge.  Madler described this area as a bright crater, 5 miles in diameter, which now it certainly is not.

LALANDE.—­A very deep ring-plain, about 14 miles in diameter, N.E. of Ptolemaeus, with bright terraced walls, some 6000 feet above the floor, which contains a low central mountain.  On the N. is the long cleft running, with some interruptions, in a W.N.W. direction towards Reaumur.

DAVY.—­A deep irregular ring-plain, 23 miles across, on the Mare E. of Alphonsus.  There is a deep crater with a bright rim on its S.W. wall, and E. of this a notable gap.  There is also a wide opening on the N. The E. wall is of the linear type.  A cleft crosses the interior.

GUERIKE.—­The most southerly member of a remarkable group of partially destroyed walled-plains, standing in an isolated position in the Mare Nubium.  Its border, on the W. and N. especially, is much broken, and never rises much more than 2000 feet above the Mare, except at one place on the N., where there is a mountain about 1000 feet higher.  The E. wall is tolerably continuous, but is of a very abnormal shape.  On the S. there is a peculiar LAMBDA-shaped gap (with a bright crater, and another less prominent on the E. side of it), the narrowest part of which opens into a long wide winding valley, bounded by low hills, extending to the W. side of a bright ring-plain, Guerike B, on the S.E.  A crater-chain occupies the centre of this valley.  There is much detail within Guerike.  A large deep bright crater stands under the E. border on a mound, which, gradually narrowing in width, extends to the N. wall; and a rill-like valley runs from the N. border towards the E. side of the LAMBDA-shaped gap.  In addition to these features, there is a shallow rimmed crater, about midway between the extremities of the rill-valley, and several minor elevations on the floor.