a shirt were generally of the same size; however, scales from different shirts varied significantly. The scales were wired together in horizontal rows that were then laced or sewn to the backing. Therefore, each scale had from four to 12 holes: two or more at each side for wiring to the next in the row, one or two at the top for fastening to the backing, and sometimes one or two at the bottom to secure the scales to the backing or to each other. It is possible that the shirt could be opened either at the back or down one side so that it was easier to put on, the opening being closed by ties. Much has been written about scale armour's supposed vulnerability to an upward thrust, but this is probably exaggerated. No examples of an entire lorica squamata have been found, but there have been several archaeological finds of fragments of such shirts and individual scales are quite common finds—even in non-military contexts. Lorica musculata Shields Scutum Parma The parma was a circular shield, three Roman feet across. It was smaller than most shields, but was strongly made and regarded as effective protection. Its strength came from its design of gluing multiple layers of wood together while stretching leather across it to eliminate the shields' vulnerability to water. This may have been due to the use of iron in its frame. It had a handle and a shield boss (umbo). The parma was used in the Roman army of the mid-Republic, by the lowest class division of the army — the velites. The velites''' equipment consisted of a parma, javelin, sword and helmet. Later, the parma was replaced by the scutum. Caetra A light shield of wood and leather, the name from Greek (καίτρεα, Hesych.). Used by tribesmen from Hispania, Mauretania, and Britannia. Helmets Roman helmets, galea or cassis, varied greatly in form. One of the earliest types was the Montefortino helmet used by the Republic armies up to the 1st century BC. This was replaced directly by the Coolus helmet, which "raised the neck peak to eye level and set a sturdy frontal peak to the brow of the helmet". The Galea was used from the late 1st century BC to the late 2nd century AD and it drew influence from the Gallic tribes to the north, hence its name. Roman helmets usually featured a bowl