360 F. H. EDGEWORTH 



the Quadrate. The Hyomandibula was always found dorsal 

 to the hgament. It is a rhombic cartilage applied at its 

 anterior edge to the ' cranial cartilage ' (apparently the otic 

 process), and with a ventral process which is attached to the 

 upper surface of the suspensorial tubercle. The ventral 

 process may be a separate cartilage. In one specimen he found 

 a small accessory cartilage embedded in the ligament. Sewert- 

 zoff (1902) stated that the Quadrate is formed independently 

 of the chrondrocranium and fuses with it by three processes 

 — a ' palatobasal ' uniting it with the trabecula, an ' ascending ' 

 uniting it with the alisphenoidal wall, an ' otic ' uniting it with 

 the external wall of the auditory capsule. He did not describe 

 any pterygoid process. A Hyomandibula is present, lying just 

 dorsal to the ligament connecting the top of the ceratohyal 

 with the Quadrate. 



K. Flirbringer (1904), in the 17-8 mm. stage, described 

 a cartilage which lies behind the Quadrate, and, internally, 

 is continuous with the anterior part of the auditory capsule. 

 At an earlier stage the cartilage is separate from the cranium. 

 This cartilage he identified as probably that described by 

 Huxley. It did not exactly correspond in position with the 

 Hyomandibula of Sewertzoff. 



Krawetz (1911) stated that two cartilages are developed 

 behind the Quadrate, one, the ' Hyomandibula ' which lies 

 in a cell-column (' Strang '), passing from the Quadrate to the 

 auditory capsule, and a second, the Symplecticum, in close 

 association with the ligament passing from the ceratohyal 

 to the otic process of the Quadrate. These two cartilages are 

 in connexion by a connective tissue, ' Strang '. The first- 

 named of these cartilages is that represented by K. Flirbringer 

 in his figures of the embryonic stage, the latter that repre- 

 sented by Sewertzoff. These two cartilages with the connecting 

 ligament represent the upper part of the hyoid bar which is 

 ' zerfallen ' into two parts. 



The statement of Krawetz that the upper part of the hyoid 

 bar is ' zerfallen ' into two parts appears to be an inference 

 only, as he does not state that a single cartilage or structure 



