34 



VESTIGIAL EPISTERNA 



CHAP. 



provided with pieces of bone which overlie the manubrium sterni 



Fia. 22. Shoulder girdle of Ornithorhynchus. c 1 , c'-, c 3 , First, second, third ribs ; d, 

 clavicle ; e.c, epicoracoid ; es'andes", interclavicle (episternum) ; m.c, metacoracoid ; 

 m.s, mauubrium sterrii ; sc, scapula ; st, sternebra. (From Wiedersheim's Structure 

 of Man.) 



and are attached to the clavicles, and are no doubt to be regarded 



as the same structure. Probably in many 

 mammals the manubrium will be found 

 to be partly made up of corresponding 

 rudiments. In any case, vestiges of an 

 episternum in the shape of two minute 

 ossicles have been discovered in Man, 

 lying in front of the manubrium. They 

 have been termed ossa suprasternalia. 

 In Man and in the Mole the paired 

 ..r.c. nature of the episternum is clearly 

 apparent. It has been suggested that 

 this structure in its entirety belongs to 



FIG. 23. Episternum of an em- the clavicles, just as the sternum belongs 

 ?ciS; fy%*Sg to the ribs ; *.* that it formed out of the 

 tion of the episternum ; es", approximated and fused ends of the 



lateral portion of the same; i i T-VH/T-J.!^ j i 



r.c, costal ribs ; st, sternum, clavicles. Dr. Mivart figured a good 

 (The figure was constructed many years since a pair of ossicles in 



from two consecutive hori- ,.- , . 



zontai sections.) (From Mycetes, lying in one case between the 

 Wiedersheim's structure of en( j s o f t he clavicles and the manubrium 



Man.) . . 



sterni, and in another example anterior 



to the ventral ends of the clavicles. Gegenbaur has figured a 

 1 Proc. Zool. Soc. 1865, p. 567. 



