THE EAR. 



11 



of the so-called ossicida aicdlMs^ and named the ynaUeus. Tlie 

 malleus becomes attached to the 'iuemhrana tympani^ by a 

 special process ; while its other extremity, which was continu- 

 ous with Meckel's cartilage in the embryo, is converted into 

 \X\Q, processus gracilis^ or Folianus^ and lies between the tym- 

 panic, the squamosal, and the periotic bones. 



In the singular lizard Sphenodon (A, Fig. 24), the anterior 

 cornu of the hyoid is continuous with the distal end of the 

 stapes, and the latter sends a cartilaginous process upward, 

 which passes into the wall of the periotic capsule, just behind 

 the proximal end of the os qiiadratum. Thus the stapes 

 stands out at right angles to the hyoid cornu, and the latter 

 becomes divisible into a sitpra-stapedlal part, and a part which 

 lies below the stapes, and answers to the styloid process, or 

 styloliycd^ of the Mammalia. The supra-stapedial part is rejv 

 resented by cartilage, or ligament, in other Saurop)sida^ but 

 seems not to ossify. In the Mammalia (B, Fig. 24), the su- 

 pra-stapedial part ossifies, becomes the inctis^ and its proximal 

 end is usually articulated by a sjaiovial joint with the malleus 

 (= quadratum). A distinct ossification, the os orhiculare^ 

 usually arises at that part of the hyoidean cartilage in which 

 the stapes and the incus unite. That part of the hj^oidean 

 cartilage which is converted into the styloid process is gen- 

 erally connected with the orhicidare by muscular fibres, which 

 constitute the stapedius rauscle. On the other hand, the pos 



SPcSSt^. 



^c 



s&Er 



Fig. 24 — Diagram of the skeleton of the first and second visceral arches in a Lizard (A). 



JIammal (B), and an Osseons Fish (C). 

 The skeleton of the first visceral arch is shaded, that of the second is left nearly nnsrhaded. 



/. First visceral arch. 3Tck. Meckel's cartilage. Art. Articulare. Qu. Quadratum. 



3rpt, Metapterygoid ; J/. Malleus ; p.g.., Processus gracilis. //. Second viscer."! arch. 



Ify. Hyoidean cornu. St. H. Stylohyal. S. Stapedius. Stp. Stapes. S. Htp. &upra- 



str.pedial. //J/. liyomandibular. The arrow indicates the fii-st visceral cleft. Pi.. The 



periotic capsule. I'tcj. The pterygoid. 



terior, or short process of the incus^ is connected by ligament 

 with that part of the periotic mass into which the styloid pre 



