By the 10th century, there were three main classes of bireme warships of the general dromon type, as detailed in the inventories for the expeditions sent against the Emirate of Crete in 911 and 949: the "ousiakon" (), so named because it was manned by an "ousia" of 108 men; the "[chelandion pamphylon" ( πάμφυλον), crewed with up to 120–160 men, its name either implying an origin in the region of Pamphylia as a transport ship or its crewing with "picked crews" (from , "all tribes"); and the "dromōn" proper, crewed by two "ousiai". In Constantine VII's "De Ceremoniis", the heavy "dromōn" is said to have an even larger crew of 230 rowers and 70 marines; the naval expert John H. Pryor considers them as supernumerary crews being carried aboard, while Makrypoulias suggests that the extra men correspond to a second rower on each of the upper-bank oars. A smaller, single-bank ship, the "monērēs" (μονήρης, "single-banked") or "galea" (γαλέα, from which the term "galley" derives), with ca. 60 men as crew, was used for scouting missions but also in the wings of the battle line.