108 



COMPARATIVE ANATOMY 



deles and certain Anura — e.g., Bombinator, Fig. 43, C), or else 

 their free edges come into apposition and fuse together (other 

 Anura, e.q., Rana, see Fig. 48, D). In Anurans the procoracoids 

 have a more transverse position than in XJrodeles, and come into 



xW 





Fig. 85b. — Pectoral Abch or the Right Side of Scdamandra maculosa, 

 considerably magnified, and flattened out. 



iS'<S', supra-scapula ; S, scapula (ossified) ; Co, coracoid ; CI, procoracoid ; a, h. 

 bony processes extending into the procoracoid and coracoid respectively ; 6', 

 glenoid cavity, surrounded by a rim of cartilage (L). 



connection with the coracoid in the mid-ventral line, thus giving 

 rise to a fenestra between the two. The whole arch is, moreover, 

 more strongly ossified, the procoracoid being covered by an invest- 

 ing bone— the clavicle. 



Reptilia. — In Reptiles the ossification is still more marked. 

 The simplest condition of the shoulder-girdle is seen in Chelonians 



(Fig. 86), in which its similarity to 

 that of Amphibians as well as to that 

 of Hatteria is at once seen : no clavicle 

 is developed. 



In other Reptiles the same general 

 plan is retained with modifications. 

 Thus in Lizards (Fig. 44) the well- 

 developed clavicle is more indepen- 

 dent of the rest of the arch and 

 becomes ossified directly, forming a 

 delicate secondary bony lamella ex- 

 tending from the scapula to the apex 

 of the episternal apparatus. But it 

 must be remembered that the un- 

 differentiated cells of which it at 

 first consists are in direct continuity with those which form 

 the scapula. Unossified spaces are left in the coracoid, giving 



Fig. 86. — Pectoral Arch of a 

 Chblonian. (Ventral view. ) 



6', scapula; Co, coracoid; Oo^, epi- 

 coracoid ; CI, procoracoid ; B, 

 fibrous band between these two 

 elements ; I^e, fenestra between 

 them ; G, glenoid cavity. 



