84 



THE STERNUM. 



[CHAP, 



sternal ribs. This mode of articulation curiously resembles 

 that at the vertebral end of the rib. The xiphisternum is 

 rather long and simple. 



In the small Tree Anteater (Cyclothurus didactylus) the 

 presternum is very broad and trilobate, sending out lateral 

 expansions behind the attachment of the clavicles to meet 

 the first pair of ribs. The hinder, narrow part of the manu- 

 brium is segmented off from the larger anterior part, and 



mst 



FlG. 42 — Side view of three mesosternal segments from a young Anteater (Myrmc- 

 copliaga tatnandua), showing the mode of articulation of the sternal ril 

 copied from Parker's figure, mst the upper or inner surface of the mesosternal 

 segment ; sy the synovial articulation between the .segments. 



resembles a mesosternal segment ; but it is in front of the 

 attachment of the second pair of ribs. The true mesosternal 

 segments are six in number, of nearly equal width, high, 

 rounded above, and compressed below, with a synovial 

 cavity between each. The sternal ribs are articulated by a 

 single oval condyle. The xiphisternum is long, stout, and 

 styliform. 



In the Armadillos' (Dasypodida) the presternum is broad, 

 and in Priodontes gigas (Fig. 44, p. 95) strongly keeled. The 

 mesosternal segments, four to six in number, are broad above, 



