Lamont is a low ridge in the surface of Mare Tranquillitatis

Mare Tranquillitatis

Mare Tranquillitatis is a lunar mare that sits within the Tranquillitatis basin on the Moon. The mare material within the basin consists of basalt formed in the intermediate to young age group of the Upper Imbrian epoch. The surrounding mountains are thought to be of the Lower Imbrian epoch, but...

 that is most likely an impact feature. It is located to the southeast of the crater Arago

Arago (lunar crater)

Arago is a lunar impact crater located in the western part of the Mare Tranquillitatis. To the southwest lies the crater Manners, and beyond are Dionysius and the Ritter–Sabine crater pair. To the southeast is the large Lamont formation that has been submerged by the mare.The rim of Arago has a...

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Lamont has the shape of two roughly concentric but incomplete rings with an inner diameter of 60 km and an outer diameter of 120 km. (The official diameter is 75 km.) Radial ridges radiate away from the center of Lamont, except in the east and west quadrants. The ridge system is only a few hundred meters in height, with a width that averages 5 km but is thicker to the southeast. This feature is only readily visible at low angles of illumination, when shadows highlight the terrain features.

This feature is associated with a mass concentration (mascon), a sub-surface region of higher-density material.