34 



VESTIGIAL EPISTERNA 



provided with pieces of boue wliieh overlie the manubriuiu steriii 



Fio. 22. — Sliouliler girille of <)riiith.oi-hi/nchus. c', c\ c^, First, second, third libs ; t7, 

 clavicle ; ex. epicoracoid ; (w' and e.s", interclavicle (e{3isternuni) ; m.c, metacoracoid ; 

 m.s, manubrium sterni ; sc, scapula ; st, sternebra. (From Wiederslieim'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 l)een termed ossa suprasternalia. 

 In ]\Ian and in the Mole the paired 

 nature of tlie episternum is clearly 

 apparent. It has been suggested that 

 this structure in its entirety belongs to 

 the clavicles, just as the sternum belongs 

 to the ribs ; i.e. that it formed out of the 

 approximated and fused ends of the 

 clavicles. Dr. Mivart^ fiijured a uood 



Fig. 23. — Episternum of an em 

 bryo Mole. (After A. Gotte. 

 (7, Clavicle ; es', central })or 

 tiou of the episternum ; es" 

 lateral portion of the same 

 r.c, costal ribs ; st, sternum 



(The figure was constructed many yeai'S since a i)air of ossicles in 



from two consecutive hori- ,,"",.. , , 



zontai sections.) (From Mycctcs, lying in oiic casc between the 

 Wiedersheitn's strvri,n-r „f gj^^^g ^f ^\^q davicles and the manubrium 



Man.) . , . 



sterni, and m another example anterior 

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



' Proc. Zool. Soc. 1865, p. 507. 



