DEVELOPMENT OF THE SKULL IN THE URODELES. 185 
fig. 5, sq, p-hy, st, vit) the facial nerve emerges, riding on the unossified part of this new 
auditory element. 
The second or “epihyal” element (e.hy), 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 (Pl. XX XIX. fig. 4, ¢.hy), 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 (s¢.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 (/.hy", h.hy’). 
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.hy*); 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 (d.hy) 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 behind 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 (Pl. XX XIX. 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.b7', e.br'); the upper part 1s 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 (4.r’). 
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 (¢.br’, c.br?); the lower piece is almost straight, the upper is gently curved, 
with the convexity forwards. The third epibranchial (¢.7°’) is nearly as large as the 
second, of the same shape, and equally ossified; but its ceratobranchial piece is a 
mere nucleus of cartilage (¢.Jr*) attached behind the joint of the second arch. 
The fourth arch (e.d7r*) 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 
all the three upper parts (¢.dr°*) and the rudimentary third ceratobranchial (¢.7*). 
The basal pieces are reduced to one very large plate and the rudiment of a second ; 
1 Tn the “Anura” the counterpart of this small keystone is a mere binding tract of simple cartilage, not 
nearly as large as the ends of the two bars which it fastens together. 
