OF THE SCAPULA IN THE BATRACHIA. 213 



from end of coracoid by cartilage, longer than pars acromialis ; 

 dividing cleft pierced horizontally, only visible when viewed 

 obliquely, 



H. pictus Ptrs. — Scapula as in H. albopunctatus. 



Example. 



Length of prsecoracoid 10 units. 



,, scapula , 25 ,, 



„ shaft 17-5 „ 



Breadth of „ (distal end) 8'8 ,, 



„ „ (middle) 2 „ 



,, pars acromialis + pars glenoidalis 8"8 ,, 



Length of supra-scapula 17"7 „ 



Text-figure 10. 



Pectoral girdle of Heleioporus pictus, X2 ; from within. 



The abnormal development of the scapula in this genus is 

 similar to that in Phyllomedusa as regards length. In Phyllo- 

 medtosa, hovfevev, the pars glenoidalis is much smaller than the 

 pars acromialis, which is sepai'ated from the head of the praecora- 

 coid by acromion cartilage ; also the dividing cleft is long and 

 broad, forming a very large central foramen, pierced vertically. 



Summary and Conclusimi. 



These data are sufficient to show that the form of the scapula 

 is remarkably stable within a genus, and that in many instances 

 it is so highl}^ characteristic that a glance at this bone alone 

 suffices to recognize the genus to which the skeleton belongs. 

 This is the ease throughout the Pipidse and Discoglossidae, and, to 

 a great extent, in other families. In the most recent families, 

 however, there are many genera conforming to one pattern of 

 scapula, which makes the character, in these cases, Avorthless for 

 diagnostic purposes. 



Of the genera which I have studied, the greatest specific varia- 

 tion occurs in Bufo ; in Hyla, which is a very large genus, there 

 is practically none. 



Although in many ways the Pelobatid genera resemble Palceo- 

 hatratchus, the Aglossa must be regarded as having the most 

 primitive type of scapula, as in Pipa, Hymen ochirus, and Xenopiis 

 the proximal end of the bone is entire. In all other genera* 



* Genera of tlie Arcifera. 



