It is now known that there are two species in Britain. One is "Natrix natrix", the original type species. It is olive green with a yellow collar or black-and-white collar. The other is the barred grass snake, "Natrix helvetica", which is grey-brown with black stripes and no collar. The difference had been noticed, but was regarded as a difference between subspecies. Both forms are protected by law: it is an offence to harm them. 