DEVELOPMENT OF THE SKULL IN THE TJEODELES. 185 



fig. 5, sq, p.ky, st, vii) the facial nerve emerges, riding on the unossified part of this new 

 auditory element. 



The second or " epihyal " element (e.hi/), is not specialized for auditory purposes 

 like the first piece;" it is a pyriform lobe of cartilage, one half larger than the 

 pharyngohyal element, but flatter ; its narrow end is free above, and is close behind the 

 projecting end of the ribbed lobe of the suspensorium ; with this part it has coalesced, 

 except at its ends. 



This part is found in the " hyo-suspensorial ligament ;" the upper piece is found in the 

 " suspensorio-stapedial." 



The next piece, the ceratohyal (PI. XXXIX. fig. 4, cJ»j), is larger than the mandi- 

 bular ramus ; it is flat, but of great solidity ; it is bent below the upper third into an 

 elbow, with a very obtuse angle ; and the part above is ossified like a flattish phalangeal 

 bone ; the apex (st.h) is soft. The lowermost flattened part is very dilated, and ends in a 

 sigmoid condyle, to which is articulated the largest and smallest hypohyal (hJii/\ h.hij-). 

 The former is outside the lesser piece ; it is a suboval plate ; the lesser piece is finger- 

 shaped with a scooped base. Attached to the largest, at its distal end, is the middle- 

 sized piece {h.hf) ; it is reniform in outline, and by its more rounded end meets its 

 fellow of the opposite side ; its " hilus " is behind. In a small space between these 

 two the basihyal {bJiy) is articulated : it is nail-shaped ; and the head is the articular 

 part. Contrary to rule, through the overgrowth of the arch, this conjugating piece is 

 thrust hcliind the junction of the two sides of the arch'. 



There are four pairs of branchial arches, lessening in size from before backwards. 

 The first of them (PI. XXXIX. fig. 4) is very similar to the ceratohyal ; it is almost as 

 long, but only half the width, and is segmented into an epi- and a cerato-branchial 

 {e.hr\c.hr^); the upper part is the larger, and is bent backwards into an obtuse 

 " elbow," where, as in the ceratohyal, its lower two fifths is ossified. Articulating with 

 this part is the ceratobranchial, which is unossified, and is a somewhat flattened rod, 

 separated from its fellow below by the second basibranchial lobe [b.br^). 



The second branchial arch is nearly as large as the first ; but both its pieces are 

 ossified, all but their ends, as phalangiform rods, which are very thick and round where 

 they meet {e.hr'\ c.hr^); the lower piece is almost straight, the upper is gently curved, 

 with the convexity forwards. The third epibranchial [e.hr'') is nearly as large as the 

 second, of the same shape, and equally ossified ; but its ceratobranchial piece is a 

 mere nucleus of cartilage [c.br'} attached behind the joint of the second arch. 



The fourth arch {e.br'^) is only a small epibranchial, half the size of the one in front 

 of it, and only ossified for two fifths of its extent. The second ceratobranchial -carries 

 aU the three upper parts {e.br-'*) and the rudimentary third ceratobranchial {c.br''). 

 The basal pieces are reduced to one very large plate and the rudiment of a second ; 



' In the " Anura " the counterpart of this small keystone is a mere binding tract of simple cartilar/e, not 

 nearly aa large as the ends of the two bars which it fastens together. 



