Sentence:  A large admiral lizard leapt up on a rail, stood on hind legs with fore legs raised like hands and watched for a moment ..., then loped down the cess-path with arms swinging and iridescent <WSD>frill</WSD> flying out like a cape ... 
Meaning of the word marked with <WSD> tags:  The relatively extensive margin seen on the back of the heads of reptiles, with either a bony support or a cartilaginous one.