212 ELEMENTAEY BIOLOGY. [XIII. 



7. The posterior cornua, or thyro-hyals ; bony, and 

 shorter and thicker than the anterior cornua : 

 attached to the posterior border of the body 

 near the middle line and diverging as they run 

 backwards. 



B. Two pairs of smaller processes formed by the 

 elongation of the anterior and posterior angles 

 of the body of the hyoid. 



e. The sternum and shoulder-girdle. 



1. Their general arrangement : they form an incomplete 

 ring round the fore-part of the trunk : this ring is 

 composed partly of bone, partly of cartilage. Note 

 the hollow (glenoid fossa) with which the fore-limb 

 articulates. 



a. The sternum : situate in the ventral median line 

 and made up of several parts : beginning behind 

 we find 



a. The odphistemum; a thin cartilage, wide behind, 

 narrow in front, where it passes into 



^. A median cartilage ensheathed in bone, the 

 sternum proper. The anterior end of the ster- 

 num unites with the posterior and internal 

 angles of the coracoids (6* 7), the inner edges 

 of which meeting in the middle line separate 

 the sternum from 



7. The omosternum, consisting of a slender, flat- 

 tened bone, terminated in front by an expanded 

 cartilage. The posterior end articulates with 

 the prsecoracoids and the clavicles. 



6. The shoulder-girdle: beginning dorsally, it ex- 

 hibits on each side 



