He is most frequently known as _Coluber natrix_, though as both words mean simply a snake, the name is inadequate. In fact, our common English snake has been rather neglected in the way of titles, the only generic name which is at all descriptive being _Tropidonotus_, so called from the keel which characterizes the scales. So he is _Tropidonotus natrix_, and _Natrix tropidonotus_, and _Natrix torquata_ of the different authors, the last-named specific presumably given on account of the collar which he wears, and which being often yellow, has gained for him the name of ‘ring snake.’ _Coluber natrix_, having so few synonymes, they are all given, in illustration of what has been already said of the perplexity of names assigned by different naturalists. And, by the way, this ‘ring’ or ‘collar’ is not an invariable mark. Sometimes the yellow is wanting altogether, and only a white collar is displayed. At the time of writing[6] there is one of these snakes at the Zoological Gardens with not the least tint of yellow on its neck; and I have before me in alcohol a very young and beautiful little specimen in which the white collar is very bright and large, and set off with deep black behind it, but there is not an approach to yellow or to a ring, the throat being pure white. His Latin specific is therefore more appropriate than his English one, the collar being always there, but not always the ring. Dr. Günther divides the whole of the Ophidia into five groups, and in briefly describing these I shall hope to conduct my readers towards a consideration of those remarkable features which will be discussed under their various heads, and which will exhibit the class as unique in their marvellous organization and physical powers. The five groups are— 1. BURROWING SNAKES. 2. GROUND SNAKES. 3. TREE SNAKES. 4. FRESH-WATER SNAKES. 5. SEA SNAKES.