214 THE VARIATION OF THE SCAPULA IN THE BATRACHIA. 



the jjars acromialis and j'^ars glenoidcdis are separated from each 

 other by a cleft, or at least a notch (Bombmator and Pseudis). 

 This character seems to be of much greater importance than 

 mere size, and corroborates the conclusion of Wolsterstorff, who 

 says* : ^^ Palceobatrachus verbindet im Systeme die Aglossa mit 

 den Akcifira/' 



In spite of generic stability the vai-iation is enormous, par- 

 ticularly in the length of the shaft. Xenopios, on the one hand, 

 in which the scapula is absent or represented by the pars 

 glenoidalis only, ranging to Phyllomedusa, Ceratophrys, and 

 ffeleioporus, in which it is enormously developed, in Heleioporus 

 being twice and a half the length of the pra^coracoid. 



It is astonishing that such a useful bone as the scapula should 

 have been overlooked for so long. The following key is based on 

 this character alone : — 



A. Proximal end of scapula entire Pipid^, 



B. Proximal end of scapula cleft. 



I. Length of scapula \ or less than \ length of prajcoracoid. Discoglossidje. 

 II. Length of scapula more than \ length of prsecoracoid. 



a. A large oval foramen pierced vertically in glenoid 



cavity; pars ^Ze?!ou^n? is greatly reduced Hxlidjs. 



b. Foramen, if pierced vertically in glenoid cavity, 



moderate or small ; often represented by a cleft 



pierced obliquely or horizontally Pelobatidjj. 



BUFONID^. 

 CXSTIGNATHIDJE. 



I am unable to find reliable family characteristics which 

 differentiate between the Pelobatidse, the Bufonidse, and the 

 Cystignathidas. 



* Op, cit. 



