They went directly across the arena toward the rocks upon the opposite side

At first I couldn’t make out the purpose of this mighty pile of rock, unless it were intended as a rough and picturesque background for the scenes which were enacted in the arena before it, but presently, after the wooden benches had been pretty well filled by slaves and Sagoths, I discovered the purpose of the bowlders, for then the Mahars began to file into the enclosure.
They marched directly across the arena toward the rocks upon the opposite side, where, spreading their bat-like wings, they rose above the high wall of the pit, settling down upon the bowlders above. These were the reserved seats, the boxes of the elect. Reptiles that they are, the rough surface of a great stone is to them as plush as upholstery to us. Here they lolled, blinking their hideous eyes, and doubtless conversing with one another in their sixth-sense-fourth-dimension language.