DEVELOPMENT OP THE SKULL IN THE UKODELES. 207 



(fig. 2, i. n). The ethmo-palatine cartilages [e.pa) have coalesced with their hinder 

 margin below ; and the palatine bones ( pa) show no tendency to apply themselves to 

 them, their proper endoskeletal correlates. The internasal cartilage (i.n. c) is now a 

 narrow truncate band with its convex margin behind, and is much reduced from its 

 former relative size. This retrograde metamorphosis is consonant with that of the para- 

 chordals and parachordal region of the trabeculse : at first there is no intertrabecular 

 structure, and only the apices of the trabeculse run to the mid line ; afterwards all the 

 hind skull is floored, and a wide internasal band appears in front of the orbits ; then, 

 in the adult, the two halves of the endocranium are only held together by a narrow 

 parachordal band behind, and a narrow intratrabecular band in front. 



The direction of the suspensorium is what it was at the fij'st, viz. forwards, as well as 

 outwards and downwards ; this is extremely unlike what we see in the Frog, where its 

 dii-ection is at first quite forwards, and then changes so as to be directed backwards 

 vei-y considerably. 



Indeed the metamorphic range, even in the Caducibranchiate Urodeles, is very small 

 as compared with that of the ordinary Anura : they do not spring from so low a root, 

 by far, and they do not rise so high, by far, as the Irogs and their kindred. 



The suspensorium, by its ascending process (fig. 6, a. p), retains its fusion with the 

 alisphenoidal wall ; but the pedicle proper (jjd) is a bulbous condyle which rolls in 

 the concavity of the basipterygoid plate (b.pg). 



The otic process (ot. p) is a thick pedate mass of cartilage, continuous below with the 

 main body of the cartilage, not affected by the quadrate bone {q), which runs forwards 

 into the pterygoid cartilage ( e.pg) a narrow filiform process. 



c. The Free Arches of the adult Neivt. 



The hinge {q. c) is a reniform and convexo-concave condyle, corresponding with the 

 sinuous condylar surface of the mandible (tigs. 3, 3°, ar. c) ; Meckel's cartilage is 

 persistent ; but the proximal part is considerably ossified by the embracing articular 

 bone, in the trough of which it lies. 



Only the ceratohyal (fig. 7, c.hy) is developed in the next arch ; it is a spatulate bar, 

 rounded above and ossified (more than halfway down) ; the rest is aflat pyriform region 

 of cartilage, the narrow end of which is attached by a hypohyal ligament to the 

 unossified end of the first basibranchial {b.hr^), which alone represents the basiliyal 

 segment. This basibranchial (h.hr^) is not segmented, but the hinder part of it is left 

 unossified ; the whole bar is a strong compressed rod. 



The remnants of both the first and second branchial arches {e.ir^, c.br^, c.hr^) are 

 attached to the soft part, the former to its middle and the latter to its end. The first 

 bar has two, almost equal, ossified segments, and is large ; the second arch is a feeble 

 bar, bowed inwards and backwards, and is only composed of the ceratobranchial 

 element (c.ir^) ; it is fastened above to a spur on the lower end of the epibranchial of 

 the first arch. 



