THE EAR. 



77 



of the so-called ossicula miditus, and named the malleus. The 

 malleus becomes attached to the membrana tympani, hy a 

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

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

 the 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 quadratum. Thus the stapes 

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

 becomes divisible into a supra-stapedial part, and a part which 

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

 stylohyal, of the Mammalia. The supra-stapedial part is rep- 

 resented by cartilage, or ligament, in other Saiiropsida, but 

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

 pra-stapedial part ossifies, becomes the incus, and its proximal 

 end is usually articulated by a synovial 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 hyoidean 

 cartilage which is converted into the styloid process is gen- 

 erally connected with the orbieidare by muscular fibres, which 

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



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



Mamma' (B), and an Osseous Fish (C). 

 The skeletol of the first viscerfil arch is shaded, that of the second is left nearly unFhaded, 



/. First visceral arch. Mck. Meckel's cartilage. Art, Articulare. Qu. Quadi-atum. 



Mpt. Metapterygoid ; M. Malleus ; p,g.^ Processus pracilis. //. Second vipcerM ir*h. 



//?/. Hyoidean coma. St. II. Stylohyal. S. Stapedius. Stp. Stapes. >i?. l:itp. ^u]>r,v 



fttTijipdial. //J/. Hyouiandibular. The an-ow indicates the first visceral cleft, /'z. ITw 



periotic capsule. Ptg. The pterygoid. 



terror, or short process of the incus, is connected by hga^ient 

 with that part of the periotic mass into which the styloid pro- 



