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Show 546 M. G. A. BOULENGER ON THE [Nov. 16, The chief condition for doing useful work was to examine the types of all the species. I am glad to say that, in this respect, we have been perfectly successful. The species of nearly all the large collections of Europe have been examined by us. M. Lataste has received, through the kindness of Prof. Schlegel, Dr. Steindachner, and M . Coulon, communication of the African Bufones of the museums of Leyden, Vienna, and Neuchatel. Both of us have studied all the specimens in the Paris Museum ; and Prof. Vaillant has kindly communicated to me in Brussels the most interesting forms of that rich collection. Prof. Cornalia has sent me all the African specimens of the Milan Museum ; and Dr. Straueh has supplied m e with very numerous specimens of Bufo viridis from various parts of Asia. Dr. Gunther has allowed me to study the specimens in the British Museum. I beg these learned gentlemen to receive m y sincere thanks. Finally, I have had at m y disposal the collection of the Brussels Museum and that of M . Lataste, which he has most liberally communicated to me. Thus, this monograph is based upon:-all the specimens of the British, Paris, and Brussels Museums, and M . Lataste's private collection ; all the African specimens of the Leyden and Milan M u seums ; many interesting specimens of the Vienna, St. Petersburg, and Neuchatel museums. The genus Bufo, as understood by me, corresponds to the family Bufonidae of Dr. Gunther, and includes the genera Schismaderma, Bufo, and Olilophus. The first two are the only genera represented in the two regions above mentioned. I admit ten species-four in the Palaearctic region, five in the ^Ethiopian, and one (Bufo viridis) inhabiting both regions. The chief characters I have used for distinguishing these species differ in some respects from those hitherto employed. Such is that taken from the subarticular tubercles under the toes, which in some species are in a single and in others in two rows. This character I have found to be quite constant in all the species but one (Bufo an-gusticeps) ; and it has been of great help to m e in a group where the forms are so closely allied and difficult to distinguish specifically. Another good character, but which cannot be used in very young specimens, exists in the relative size of the tympanum. I have paid but little attention to the size and shape of the parotoid glands, as I am convinced that they do not afford any good specific characters, being subject to considerable variation. Whenever I have been able to examine the skeleton of a species, I have given a short account of it, restricted to those characters only that are of some interest as distinguishing the species. By the following dichotomicai key I have tried to facilitate the determination of the species; I must say, however, that it can only be applied with security to specimens which are adult, or nearly so. 1. Subarticular tubercles under the toes in a single row 5. Subarticular tubercles in two rows (most of them) 2. 2. First finger not extending beyond second . 4. First finger extending beyond seeond 4. B. mauritanicus. |