Thank you for this information. I seached for the book at amazon but it's very expensive. Do you know if the book "Texas Snakes: a field guide" by the same authors has the same information about the hognose snakes - or is it a strongly shortened version of the first book?
As regarding Acrantophis it think they are again classified as Acrantophis and not as Boa but I'm not 100% sure about it.