560 THE NATUEAL HISTORY BEVIEW. 



sternal structures, any more tlian the small size of the piece of bone 

 attached to the acromion only by a ligament, need be held to cast a 

 doubt upon their representing the clavicle. It must be admitted 

 also, that in other classes the clavicles and episternals alike present 

 degradations of a similar character, as may be seen amongst the 

 Edentata in Mynnecopliaga didactyla and Chlamydopliorus truncatus, 

 where the episternal is still tense and of moderate length ; but does 

 not appear to contain any more solid parts in its interior. 



In the flying mammals I have long sought in vain for the various 

 parts of the bony girdle of' the chest, so well known to me in other 

 mammals ; and I drew the conclusion from their absence that a more 

 intimate connection of the episternals with the sternum occurred, and 

 consequently that the broad manubrium sterni of these animals re- 

 sulted from the fusion of these parts.* The recent discovery of a struc- 

 ture that indubitably belongs to the series of episternal structures 

 in these creatures has, however, changed my opinion on this point. 



If the sterno-clavicular articulation of a Cheiropterous animal 

 is examined from before, the well-marked clavicle is seen to run 

 to the side of the manubrium sterni, and covered with cartilage, to be 

 inserted into a depression of the manubrium, which also possesses a 

 cartilaginous investment. No intermediate piece of any description 

 intervenes, and consequently the usual episternal fragment seems 

 in this instance to vanish with the appearance of a more highly 

 developed clavicle. On making an examination of the internal sur- 

 face of the articulation, however, it may be seen that the whole of 

 the terminal surface of the clavicle is not implicated in the formation 

 of the joint, but that its posterior and inferior part gives attachment 

 to a conical ligament which is connected with the sternum. The 

 ligament lies imbedded to some extent in the capsular ligament, in- 

 creasing its strength, but it is important to observe that it originates 

 directly and immediately from the clavicle itself. Its position, 

 therefore, quite independently of its magnitude, which is only a 

 secondary consideration, clearly indicates that this fibrous band is to 

 be placed in the category of the true episternals. In Pteropus a 

 similar conformation of parts is present. The episternals of Quad- 

 rumana and Man are much less highly developed. 



* The examiiintioii of the eml)ryos of the Cat exhibit a division of the manu- 

 brium sterni from the body of the sternum exactly at the point of junction of the 

 first rib. In adult Eh'mnluphi I have been unable to remark anything particular on 

 this point. VeaiJertUh Dctuheutuni is, however, provided with an articulation at 

 this part of the formation, of which the ribs on both sides participate. 



