At a distance again of 50 feet from the hastati, and facing them, they encamp the allied cavalry, starting from the same line and ending on the same line.
As I stated above, the number of the allied infantry is the same as that of the Roman legions, but from these the extraordinarii must be deducted; while that of the cavalry is double after deducting the third who serve as extraordinarii. In forming the camp, therefore, they proportionately increase the depth of the space assigned to the allied cavalry, in the endeavour to make their camp equal in length to that of the Romans.
These five streets having been completed, they place the maniples of the allied infantry, increasing the depth in proportion to their numbers; with their faces turned away from the cavalry and facing the agger and both the outer sides of the camp.
In each maniple the first tent at either end is occupied by the centurions. In laying the whole camp out in this manner they always leave a space of 50 feet between the fifth troop and the sixth, and similarly with the companies of foot,
so that another passage traversing the whole camp is formed, at right angles to the streets, and parallel to the line of the tribunes' tents. This they called quintana, as it runs along the fifth troops and companies.
Walbank Commentary