Dr. A. Giinther on the Tailless Batrachians. 63 



of the sacral vertebra has upon the mode of life is difficult to explain, 

 as it does not absolutely correspond with other physiological or ana- 

 tomical characters. By the dilatation of these processes the pelvis 

 obtains much more firmness ; and a lateral motion is more or less 

 entirely impeded. We should therefore expect to meet with this 

 character in those Batrachians which are provided with the longest 

 and most powerful hind legs, according to the physical problem, 

 that the longest lever requires the strongest centre. But on the 

 contrary, the Batrachians with the shortest legs exhibit a much-dilated 

 sacral vertebra, whilst on the other hand the long-legged HylidcB 

 show the same peculiarity. In fact, this osteological form seems to 

 be connected with none of the modifications of locomotion \ for we 

 find among these Batrachians good swimmers as well as bad, tree- as 

 well as earth-frogs, those which always hop as well as those which 

 often crawl ; finally, we are unable to refer to it a peculiarity of any 

 part of the propagation. Generally, I can only state — 



1 . That all the Batrachia anura without maxillary teeth exhibit 

 dilated processes of the sacral vertebrae, except the Hylaplesidae ; 

 but that, on the other hand, the Batrachia anura with maxillary 

 teeth may have this bone sometimes dilated, and sometimes cylin- 

 drical in form. 



2. That all the Batrachia anura with paratoids exhibit dilated 

 processes (without any exception at present) ; but that, on the other 

 hand, the Batrachia anura without paratoids have either this bone 

 dilated or cylindrical in form. 



From the above inquiries it is evident that I do not think this 

 anatomical character fit for separating the whole group of the Opis- 

 thoglossa, so as to form two natural divisions ; and there remains only 

 the third of the above-mentioned characters, — the dilated or not di- 

 lated tip of the fingers and toes. 



This natural character is connected with a strongly marked di- 

 stinction in the mode of life, with climbing trees, which peculiarity 

 is justly considered as one of the most important characters among 

 the Vertebrata. No frog or toad without dilated toes is known to 

 climb trees ; and although our knowledge of the mode of life of 

 the tropical forms is very limited, I have no doubt that the tooth- 

 less Batrachians with dilated toes, of the tropics (^Hylaplesia, Hy- 

 Icedactylus, Brachymerus, &c.), are enabled to climb trees, walls, 

 &c., some being active during the day, others during the night. 

 I am well aware that there are forms having the toes so slightly di- 

 lated that it is difficult to say to which section they belong ; but in 

 such instances the question will be decided either by observation of 

 the living animals or by the more distinguishable form of closely 

 allied species, as for example in the genus Hylodes. The objection 

 to separating the toothless Batrachians in this way, they having 

 been till now considered as a natural group, I get over by the fact 

 that my two proposed series are parallel, and their members nearly 

 corresponding ; and I trust that at a not far distant time some of the 

 wanting forms will be found. Therefore I divide the Anura opistho- 

 glossa into two series : — 



