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established groups. Especially I think we can thus satisfy the long- 

 felt necessity of separating the Bombinatores in a strictly circum- 

 scribed group. Now-a-days a group, defined as Tschudi does the 

 Bombinatores, " Body and extremities short, head rounder than in 

 the Ranae, skin generally warty,''' is not fit to form a part of the 

 natural system. Huschke was the first who directed the attention 

 of naturalists to a peculiarity in the ear of Bombinator igneus, 

 stating, in the ' Beitrage zur Naturgeschichte unci Physiologie,' p. 39, 

 " Not much of a cavum tympani is to be seen in Bufo igneus, whereas 

 muscles of the ossicula auditus appear to fill up the whole space." 

 This information was not much enlarged by the inquiries of Geoffroy, 

 Scarpa, and Windischmann ; but Johannes Midler, having found a 

 similar structure in the ear of the Pelobates of France (P. cultripes), 

 with his anatomical ingenuity applied this character for a distribu- 

 tion of the Tailless Batrachians into three groups : — 



1 . Anura with an entirely bony cavum tympani, with a cartilagi- 

 nous cover of this cavity instead of a membranaceous tympanum, 

 with the Eustachian tubes united into a single aperture : Dactyle- 

 thra and Pipa. 



2. Anura with a partially membranaceous cavum tympani, with a 

 membranaceous tympanum and the apertures of the Eustachian tubes 

 separated : the greater part of the Anura. 



3. Anura without tympanum, eustachian tubes, or cavum tympani, 

 and with the cover of the fenestra ovalis cartilaginous : Bombinator 

 igneus and Pelobates cultripes. 



In rejecting this systematical arrangement of the whole suborder, 

 I agree so far with Tschudi, not, however, " because the anatomist 

 ought not to prescribe divisions to the zoologist," but rather because 

 the Batrachians with imperfectly- developed ear wovdd form together 

 an unnatural group, and would be separated too far from other allied 

 forms, if we tried to apply this character as that of a section. On the 

 other hand, it is much more important than Tschudi supposes, because 

 it proves to be of absolute value, as always indicating the total ab- 

 sence of the tympanum. Batrachians with well-developed ear exhibit 

 sometimes a conspicuous, sometimes an indistinct, sometimes a hidden 

 tympanum, which differences may offer in some cases a generic, in 

 others only a specific character ; even in many instances the appear- 

 ance of the tympanum is variable in the individuals of the same 

 species, being more or less conspicuous. The tympanum is hidden 

 in those Batrachians where it is formed by a transparent membrane ; 

 but the skin of the body, not modified and not adherent, equally 

 covers the tympanic region, and the tympanum becomes visible only 

 after the skin is removed. The tympanum is indistinct in those 

 Batrachians where the skin of the body is firmly adherent to the 

 tympanum, covering more or less of its surface. But in all these 

 Batrachians the tympanum is present ; and it is a great mistake to 

 confound the characters of a hidden and of an absent tympanum ; 

 and much trouble and much misunderstanding would be saved to 

 naturalists, if a more precise mode of expression were introduced 



