72 SKELETON OF THE FROG. 



are present and long on the rest, especially on the third, 

 c?, and ninth, s, vertebrte; in the latter they are thick, 

 stand outwards, and support two other long, curved, rib- 

 like bones, 62, which expand at their distal ends, and 

 unite to two bony plates, 63, completing the hcTemal arch 

 of the ninth segment of the trunk. The bones of the 

 hinder extremities are attached to the point of union of 

 the above costal and h^mal pieces, one of which answers 

 to the ilium, 62, and the other to the ischium, 63. The 

 superior development of this arch relates to the great 

 size and strength of the hinder extremities in the tailless 

 tribe. The bodies of the vertebrse are articulated by 

 ball-and-socket joints, the cup being anterior, the ball 

 posterior, a modification which relates to the more ter- 

 restrial habits and locomotion of these higher-organized 

 batrachia. The caudal vertebrae are represented by a 

 single, elongated, cylindrical style, c, having an anchy- 

 losed neural canal. In the seven vertebras, between the 

 atlas and the sacrum^, two zygapopophyses, looking up- 

 wards, two zygapophyses, z, looking downwards, and a 

 short spine, are developed from each neural arch. 



The suprascapula, 50, is very broad, and in great part 

 ossified ; the scapula, 51, divides at its humeral end into 

 an acromial and coracoid process ; the latter articulates 

 with the true coracoid bone, 52, the acromion with the 

 expanded extremity of the clavicle, 58 : the glenoid 

 cavity is formed by both the scapula and the coracoid. 

 An episternal bone, 59, supporting a broad cartilage, is 

 articulated to the mesial union of the clavicles, from 

 which a bony bar is continued backwards between the 

 expanded and partially conjoined ends of the coracoids. 

 The sternum, 60, is articulated to the posterior part of 



