A new species of boa constrictor with silvery scales has been discovered on a remote island in the Bahamas.
Scientists identified 20 of the three-foot long snakes during two expeditions to the Caribbean islands, the second made in October last year.
One of the creatures made a dramatic appearance by slithering onto the head of the expedition leader as he slept.
The Silver Boa, Chilabothrus argentum, is so-named because of its distinctive silver colour and the fact that the first specimen found was climbing a Silver Palm tree.
The US team led by Dr Graham Reynolds, from Harvard University, confirmed that the snake was a previously unknown species after conducting a genetic analysis of tissue samples.
Commenting on the find, boa constrictor expert Robert Henderson, from the Milwaukee Museum of Natural History in the US, said: "Worldwide, new species of frogs and lizards are being discovered and described with some regularity. New species of snakes, however, are much rarer.
"Graham Reynolds and his co-authors have not only discovered and described a new species of snake, but even more remarkable, a new species of boa. That's rare, exciting and newsworthy.
"The beautiful Bahamian Silver Boa, already possibly critically endangered, reminds us that important discoveries are still waiting to be made."
A report from Harvard University described how, during the first expedition, one of the snakes introduced itself to Dr Reynolds while he and his colleagues were sleeping on a beach.
"As Dr Reynolds slept, a boa crawled down from the forest, across the beach and directly onto his head," the report revealed.
"This caused him to awake with a start, and upon realising what had happened, he awoke the others to inform them that they had found their sixth animal."
Captured Silver Boas were electronically tagged by the scientists before being freed back into their forest home.
The creature is said to be critically endangered according to the International Union for Conservation of Nature's "Red List" criteria, and threatened by feral cats that roam the island.
A paper describing the Silver Boa is published in the journal Breviora.