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 examiued by us. M. Lataste has 

 received, through the kindness of Prof. Schlegel, Dr. Steiudachner, 

 and M. Coulon, communication of the African Bufones of the mu- 

 seums 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 speci- 

 mens of the Milan Museum ; and Dr. Strauch has supplied me with 

 very numerous specimens of Bufo viridis from various parts of Asia. 

 Dr. Giinther has allowed me to study the specimens in the British 

 Museum. I beg these learned gentlemen to receive my sincere 

 thanks. Finally, I have had at my disposal the collection of the 

 Brussels Museum and that of M. Lataste, which he has most libe- 

 rally communicated to me. 



Thus, this monograph is based upon : — all the specimens of the 

 British, Paris, and Brussels Museums, and M. Lataste's private col- 

 lection ; all the African specimens of the Leyden and Milan Mu- 

 seums ; many interesting specimens of the Vienna, St. Petersburg, 

 and Neuchatel museums. 



The genus Bufo, as understood by me, corresponds to the family 

 Bufonidse of Dr. Giinther, and includes the genera Schismaderma, 

 Bufo, and Oiilophus. The first two are the only genera represented 

 in the two regions above mentioned. I admit ten species — four 

 in the Palsearctic region, five in the J<lthiopian, 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 me 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 tlie size and shape of the parotoid glands, 

 as I am convinced that they do not afford any good specific cha- 

 racters, being subject to considerable variation. 



Whenever I have been able to examine the skeleton of a species, 

 I have given a sliort account of it, restricted to those characters only 

 that are of some interest as distinguishing the species. 



By the following dichotomical 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. 



Subartic-ular tubercles in two rows (most of them) 2. 



2. First finger not extending beyond second 4. 



First finger extending beyond second 4. B. mauritanious. 



