io2 THE STERNUM. [CHAP. 



pair of ribs are attached, and a xiphisternum (xs). The 

 second, third, and fourth pairs of sternal ribs are attached 

 to the intermediate unossified portion, representing a rudi- 

 mentary mesosternum. 



In the Manatee (Manatus) the sternum is of somewhat 

 similar form, and has three pairs of ribs attached to its 

 lateral margins near the middle. 



Among the EDENTATA there is considerable variation in 

 the characters of the sternum. 



In the Cape Anteater (Orycteropus) the sternum is of 

 quite a normal form. The presternum is trefoil-shaped, 

 expanding laterally near the front to meet the largely 

 developed clavicles, then contracting to the width of the 

 mesosternal segments, which are four in number, simple, 

 flattened, oblong, with lateral margins nearly parallel, 

 rather broader above than below, united together by fibrous 

 tissue, and succeeded posteriorly by a moderately developed 

 xiphisternum. 



In Manis aurita the sternum is flat, consisting of seven 

 segments, several of which are sometimes divided in the 

 middle line by synovial cavities. The xiphisternum is 

 very long, partially cleft in the middle line, and ending in 

 a large flattened cartilaginous expansion. In the Long- 

 tailed Pangolin (Manis macrura] the xiphisternum is of a 

 remarkable form, being prolonged into a pair of cartila- 

 ginous processes, each about nine inches long, and con- 

 nected posteriorly with some rudimentary abdominal ribs. ' 



In the Anteaters (Myrmecophaga) the presternum is broad, 

 flat, and oval. The segments of the mesosternum (Fig. 43) 

 are eight in number, short, deep, broad above, and sending 

 a club-shaped process downwards ; each is ossified from a 

 principal endosteal centre and eight epiphyses, is connected 



1 Parker, op. fit. p. 208. 



