222 THE ANATOMY OF VERTEBRATED ANIMALS. 



tongue ; and, usually, of two long cornua on eacli side of 

 this. The cephalic ends of the anterioi- cornua may be per- 

 fectly free, and lie upon the sides of the neck, as in Psain- 

 mosaui'us ; or they may be traceable to, and be connected 

 with, the stapes and the parotic processes, as in Sphenodon. 



The limbs may be completely developed ; or only one pair 

 (either the anterior or the posterior) may be present; or they 

 may be entirely absent. When present, they may be mere 

 styliform rudiments, or may possess any number of digits 

 from two to five. Even when the limbs are altogether 

 absent, the pectoral arch remains, thoiigh the pelvic arch 

 seems to vanish. When the pectoral arch is complete, it con • 

 sists of a suprascapula, scapula, coracoid (with precoracoid 

 and epicoracoid elements), and two clavicles, united by an 

 interclavicle, which lies in a groove of the sternum. (Figs. 

 12 & 13, pp. 35 & 36.) 



The coracoids articulate with grooves in the anterolateral 

 edges of the sternum, and usually more or less cross and 

 overlap one another, in front. 



In the genus Lialis, in which not a trace of a fore-limb is 

 discernible, there is a small sternum, consisting of a flat, 

 somewhat pentagonal, plate of cartilage, in which there is a 

 little coarsely gi-anular calcareous deposit ; but this sternum 

 is connected with nu ribs, nor, though it lies between the 

 coracoids, does it articulate with them. Each coraco- 

 scapular arch is a continuous cartilage, narrow in the 

 middle, but expanded at its dorsal, and still more at its 

 sternal, end, where the right overlaps the left, and both are 

 connected by fibrous tissue with the sternum. The narrow 

 middle part of the coracoid is invested, and in part replaced, 

 by a sheath of membrane bone, which expands above and 

 below, and represents both scapula and coracoid, though it 

 presents no trace either of division, or of a glenoidal cavity. 

 Beyond the extremities of this central ossification the carti- 

 lage merely presents scattered granular calcification. Along 

 the front edge of each coraco- scapular arch, and closely con- 

 nected with its ossified part, is a long curved clavicle, en- 

 tirely composed of membrane bone, and united with its fellow 



