OF THE SCArULA IN THE GATRACHIA. 203 



head of praecoracoid are thin almost to transparency, forming a 

 semicircular crest, the diameter of which follows the free upper 

 edge. 



The proportions of the scapida are remarkably stable within 

 the genus Bombinator, and are highly characteristic. 



Alytes Wagl. 



A. obstetricans Laur. — Scapula short, but less reduced than in 

 Discoglossus and Bombinator. Upper border forming a semi- 

 circular crest thin to transparency, resembling Bombinator maxi- 

 mus in this respect. Shaft reduced ; pars acromialis narrow, in 

 contact with head of prascoracoid ; pars glenoidalis broad, 

 depressed, equal in length to pars acromialis ; the two over- 

 lapping, so that the dividing cleft is pierced horizontally and 

 only visible obliquely. 



Example. 



Length of praecoracoid 10 units. 



,, scapula (lower edge) 4"3 ,, 



(upper „ ) 3-6 „ 



„ shaft 2-2 „ 



Breadth of ,, (distal end) 4' 3 ,, 



Length of supra-scapula 10 ,, 



Pelobatiile. 



In this family there is a. wider generic diversity in the propor- 

 tions of the scapula, which is not, however, greatly developed in 

 any genus. In all, the glenoid cavity is excessively deep, some- 

 what undermining the pars acromialis, the lower edge of which 

 circumscribes it above. 



Scaphiopus Holbr. 



S. solitarius Holbr. — Scapula well developed, longer than 

 praecoracoid ; as long as the supra-scapula. Proximal end well 

 developed, subcircular. Shaft long, wedge-shaped ; pars acromialis 

 large, with crest-like upper border, lower border projecting over 

 and round glenoid cavity in a strong ridge ; pars glenoidalis 

 small, strongly depressed, the dividing cleft short and broad, 

 forming a small oval foramen in the glenoid cavity, pierced 

 vertically. 



Example. 



Length of praecoracoid 10 units. 



,, scapula (upper or lower border)... 13 ,, 



„ „ shaft 9-4 „ 



Breadth of „ (distal end) 5-3 ,, 



„ (middle) 2-5 „ 



Length of supra-scapula 13 ,, 



Proc. Zool. Soc— 1921, No. XV. 15 



