underwater rocks. Authors have suggested that it was introduced into the Mediterranean by Arabs, possibly with an ultimate origin in India. The discovery of new depictions and literary references in recent decades has led scholars to antedate the appearance of the lateen sail in the Levant to the late Hellenistic or early Roman period. Not only the triangular, but also the quadrilateral version were known, used for centuries (mostly on smaller craft) in parallel with square sails. Belisarius's fleet during the Vandalic War, as described by Procopius of Caesarea, was apparently at least partly fitted with lateen sails, making it probable that by that time the lateen had become the standard rig for the dromon, with the traditional square sail gradually falling from use in medieval navigation. These 6th-century dromons were single-banked ("monoreme") ships of probably 50 oars, arranged with 25 oars on each side. Again unlike Hellenistic vessels, which used an outrigger, these extended directly from the hull. In the later two-banked ("bireme") dromons of the 9th and 10th centuries, the two oar banks (elasiai) were divided by the deck, with the first oar bank below and the second oar bank above deck; these rowers were expected to fight with the ship's marines in boarding operations. The Greek scholar Christos Makrypoulias suggests an arrangement of 25 oarsmen beneath and 35 on the deck on either side for a dromon of 120 rowers. The length of these ships was probably about 32 meters. Most contemporary vessels had a single mast (histos or katartion), the larger bireme dromons probably needed at least two masts to maneuver, assuming that a lateen sail for a ship this size would have reached unmanageable dimensions. The ship was steered by means of two quarter rudders at the stern (prymnē), which also housed a tent (skēnē) that covered the captain's berth (krab(b)at(t)os). The prow (prōra) featured an elevated forecastle (pseudopation), below which the siphon for the discharge of Greek fire projected; secondary siphons could also be carried amidships on either side. A pavesade (kastellōma), on which marines could hang their shields, ran around the sides of the ship, providing protection to the deck crew. Larger ships also had wooden castles (xylokastra) on either side between the masts, similar to those attested for the Roman liburnians, providing archers with elevated firing platforms. The bow spur (peronion) was intended to ride over an enemy ship's oars, breaking them