VARIATION OF THE SCAPULA IN THE BATRACHIA. 197 



10. On the Variation of the Scapula in the Batvachian 

 Groups Aglossa and Arcifera. By Joan B. Procter, 

 F.Z.S. 



[Received October 29, 1920 : Read March 8, 1921.] 

 (Text-figures 1-10.) 



The variation of the scapula in the Batrachia Ecaudata is of 

 considerable interest, both on account of its wide range and of 

 its comparative stability within a genus. The present study has 

 been confined to the Aglossa and the Arcifera as representing the 

 most primitive types now living. I have examined all the 

 skeletons in the collection of the British Museum, but this 

 material, although large, is not as complete as one could wish. 



Bufo licematiticus. X2. 

 (a) Pectoral girdle from without ; (b) scapula from within. 



p. a., pars acromialis. p.g., pars glenoidalis. sh., shaft, sup. art., superficial 

 articulation, f. a., fovea acetabulum, c.f., central foramen, p.c, paraglenoid 

 cartilage. 



In the majority of species the scapula is about equal to the 

 prsecoracoid in length ; it is usually rather slender in the middle 

 and expanded at each end. The proximal end consists of two 

 parts, generally separated by a clef t : the upper or pars acromialis 

 is either in contact with the head of the praacoracoid, or narrowly 

 separated from it by acromion cartilage ; the lower or pars glenoi- 

 dalis is much depressed and concave, forming the bottom of the 

 glenoid cavity — it may be in contact with the end of the coracoid, 

 or separated from it by paraglenoid cartilage. This cartilage also 

 forms a subtriangular knob projecting below the head of the 

 praecoracoid, and attached to the head of the humerus by a liga- 

 ment. The portion of the scapula between the glenoid cavity 



