Wikipedia
A horse-bus or horse-drawn omnibus was a large, enclosed and sprung horse-drawn vehicle used for passenger transport before the introduction of motor vehicles. It was mainly used in the late 19th century in both the United States and Europe, and was one of the most common means of transportation in cities. In a typical arrangement, two wooden benches along the sides of the passenger cabin held several sitting passengers facing each other. The driver sat on a separate, front-facing bench, typically in an elevated position outside the passengers' enclosed cabin. In the main age of horse buses, many of them were double-decker buses. On the upper deck, which was uncovered, the longitudinal benches were arranged back to back.
Similar, if smaller, vehicles were often maintained at country houses (and by some hotels and railway companies) to convey servants and luggage to and from the railway station. Especially popular around 1870-1900, these vehicles were known as a 'private omnibuses' or 'station buses'; coachman-driven, they would usually accommodate four to six passengers inside, with room for luggage (and sometimes additional seating) on the roof.
A small open wagon with or without a top, but with an arrangement of the seats similar to horse-drawn omnibuses, was called a wagonette.