550 



THE NATURAL HISTORY REVIEW. 



applied to the manubrium sterili, which is here broad and expanded 

 anteriorly, and supports the first pair of ribs. The azygous median 

 portion, which was present in the E-odentia (in Qmlogenys and 

 Cavid), is altogether deficient, the two lateral parts alone appearing, 

 which it is impossible from the evidence already adduced to admit as 

 having a more intimate relation with the clavicle, however likely it 

 might appear from an imperfect knowledge of these parts. These 

 cartilaginous pieces are certainly not simply detached portions of the 

 clavicles, or autogenously developed epiphysial cartilages, but are on 

 the contrary portions of the skeleton, primarily separate and distinct 

 from the clavicle. Each episternal cartilage presents a cup-like 

 excavation for the reception of the sternal end of the clavicle, which 



Fig. 3. 



Episternal apparatus of M'us 7)msculns: — st, sternum; ep, episternum; cl, clavi- 

 cle ; CO', coracoid ; c, tirst rib. 



is itself invested with cartilage, and constitutes a kind of articular 

 cavity. The perichondrium of the episternal cartilages is directly 

 continuous with the periosteum of the clavicles, and represents there- 

 fore the capsular ligament of the joints between them. The epi- 

 sternal cartilages are somewhat constricted about the middle of their 

 length, and are applied to the sternum by thick rounded extremities. 

 The investment of connective tissue is here only loosely attached to 

 the sternum by the more superficial layers, whence a considerable 

 amount of mobility is permitted both in the episternal pieces and 

 in the clavicles. The distance between their points of attachment to 

 the sternum is about one-half the length of the episternals themselves. 

 The episternal pieces appear to retain their hyaline cartilaginous 

 character for a considerable period, for even in apparently full-grown 

 specimens I sometimes found them without any discoverable trace of 

 ossification, and presenting the same appearances as in young indi- 



