Ret"ia, Pecten and Spondylus, [114]

Ret"ia, upright compound, [72]

Ret"ia, upri"ht simple, [69]

Rhabdites, [69], [81]

Saccus vasculosus, [244], [322]

Scales, [345]

Scaphaspis, [349]

Schwann, sheath of, [469]

Sclerotomes, [388]

Scorpion, brain, [54]