. a. c. 



(^ THE FROG. PHYLUM CHORDATA 



the qiKulratc. known as the mandibular fossa. Meckel's cartilage 



appears also to be in contact with the quadrate. 



Yhv hyoid (Fig. 271) is a flat structure in the floor of the mouth. 



It consists of a wide body with two 

 short processes on each side and two 

 longer processes, the cornua, at each 

 end. The anterior cornua are very 

 long and slender and curve back- 

 wards at the sides of the body and 

 then upwards to be attached to the 

 sides of the auditory capsules. The 



Fig. 271.— The hyoid apparatus posterior cornua are shorter and 

 of a rog stouter and project backwards at 



(I. c. Anterior cornua ; b., body , J^ J _ 



p.c, posterior cornua. j-j^g sidcs of the wiudpipc. They 



are the only ossified parts of the hyoid, the remainder con- 

 sisting of cartilage. The hyoid, the columella auris, and the 

 cartilages of the larynx probably represent the branchial arches 

 of fishes. 



LIMB GIRDLES 



The pectoral or shoulder girdle (Fig. 272) is a flattened structure 

 of cartilage and bone embedded in the body-wall of the forepart 

 of the trunk, which it almost encircles. It consists of two similar 

 halves, one on each side of the body, united below but separate 

 above, where they are bound by muscles to the backbone. Each 

 half is composed of an upper scapular portion or shoulder blade 

 and a lower coracoid portion. The uppermost part is a broad. 

 Hat plate lying on the back known as the suprascapula. A great 

 part of this consists of cartilage stiffened by calcareous matter, 

 but it has a narrow rim of plain cartilage and a patch of true 

 bone lies upon it where it joins the scapula, a narrower but stouter 

 bone placed at the side of the body. A forward projection from 

 this bone is known as the acromion process. To the lower end 

 of the scapula is attached the coracoid portion of the girdle. 

 This is a plate of cartilage and bone lying on the under side of 

 the body in the breast region and pierced by a wide oval space 

 called the coracoid fontanelle. Behind the fontanelle lies the stout 

 coracoid bone ; in front is a narrow strip of calcified cartilage, 

 sometimes miscalled the precoracoid, continuous with another 

 :tnp known as the epicoracoid which forms the inner border 



