2o8 . AYERS AND JACKSON. [Vol. XVII. 



extremity the palatine bar is connected by a short process with 

 the corresponding trabecula. The main bar of the palatine 

 passes directly backward and downward into the anterior 

 process of the pterygo-quadrate. 



The posterior division of the palato-pterygo-quadrate carti- 

 lage is \hQ pterygo-quadrate (Figs. 5, 6, 7, PQ). This cartilage 

 is triradiate, being composed of three large flattened processes, 

 the anterior, the superior, and the inferior. The anterior process 

 runs forward, upward, and inward, to fuse with the posterior 

 end of the palatine bar. It is flattened and slightly curved, its 

 outer surface looking outward, upward, and slightly forward. 

 Posteriorly it fuses into the superior and inferior processes. 

 The superior process is a flattened bar passing upward, back- 

 ward, and inward. On reaching the level of the cranial floor 

 it passes inward and slightly forward and fuses with the tra- 

 becula just in front of the auditory capsule. The anterior 

 margin of the superior process, the upper margin of the 

 anterior process, and the external margin of the trabeculae 

 together enclose a large oval fenestra (i). The anterior and 

 superior processes together constitute the subocular arch. In 

 its upper portion the superior process gives off posteriorly a 

 large flattened connecting piece which runs directly backward 

 to fuse with the hyoid arch, a short distance from the auditory 

 capsule. The posterior margin of the superior process and 

 the superior margin of the connecting piece are separated from 

 the external wall of the auditory capsule by a narrow, curved 

 fenestra (2). The inferior process runs outward, downward, 

 and backward, enlarging at the lower extremity, where it fuses 

 with the hyoid arch. The inferior process is flattened laterally. 

 Its upper margin, together with the posterior margin of the 

 superior process, the inferior margin of the connecting piece, 

 and the anterior margin of the hyoid arch, encloses a large 

 fenestra (3) nearly circular in general outline. 



The hyoid arch (PI. XXII, Figs. 5, 6 ; PI. XXIII, Fig. 7, Hy) 

 is a flattened, irregular, vertical bar placed behind the pterygo- 

 quadrate. The upper end fuses with the posterior half of the 

 external wall of the auditory capsule. From the point of 

 fusion the hyoid arch extends outward and downward, almost 



