\. 



DEVELOPMENT OF THE SKULL IN THE BATRACHIA. 21 



Its fore margin sends out a snag ; another follows this near the condyle for the 

 lower jaw, and opposite tliis is a third, which has been described as tied by a ligament 

 to the cornu trabecuke. 



The apex of the orbitar process rests npon a longitudinal crest of the palato- 

 pterygoid band; this is the rudiment of the post-palatine (^Ji.^^a.) ; it projects, now, 

 into the subocular space. 



The whole of the structure just described is not merely an hypertrophied epi-visceral 

 element, it has given rise to a large extya -visceral outgrowth. 



The " cerato-visceral " element is one-third the length and one-third the breadth of 

 its own upper piece — but it is thicker ; this is the free mandible or Meckel's cartilage 

 {mk.). This bar is strongly curved, having a long, terete, angular process behind its 

 condylar face, which is a deep notch, like that of the human ulna. The shaft of 

 the cartilaofe is both dilated and thick, and its subconcave end articidates with 

 one side of the large sucking disk, the corresponding inferior labial {J. I.). 



This huge, almost horizontal mandibular arch, with its free bars turned inwards at 

 little more than a right angle, is flush, in front, with the trabecular end of the 

 chondrocraiiium. 



The four points of attachment to the basis-cranii of this long suspensorium shows a 

 modified condition of that complete fusion of the two regions seen in the Chimroroids. 



In Dactylethra (ibid., Plate 5G) this state of things is intensified, and in Pipa 

 (ibid., Plate 60, fig. 3) the membranous space between the basal and lateral cartilages 

 is reduced to a small crescentic slit. 



The larval Ranine skull may therefore be said to be, in this respect, a specialisation 

 and dissection, so to speak, of the Chimferoid type of skull ; on the whole, it is much 

 more like that of the Lamprey. 



This immense development of the first epi-visceral element is correlated with the 

 suppression of all those that should succeed ; only afterwards, when this part has been 

 relatively lessened, and greatly modified, does even that of the next succeeding %i-ch 

 appear, not then as a mere facial bar, but speciahsed to auditory purposes, as the 

 " columella." 



But the " cerato-hyal " (Plate 2, fig. 7, c.hj.) is at present very large, several times 

 larger than its covmterpart of the mandibular arch (mk.). 



It has a dilated, fan-shaped distal expansion (fig. 7), a gently convex pyriform 

 condyle (hij.c.), and a curved upper spike, the rudiment of the stylo-hyal {st.h.) or 

 upper end of the bar. The basi-hyal {h.hy.) is still membranous, but it is followed by 

 a solid basi-branchial (h.hr.) ; these parts will be described in a con-esponding lai-va of 

 R. jnpiens, and in a riper larva of this same species. 



The ossifications in this stage are, first, a roundish patch of bone on each siile, 

 formed in the substance of the cartilage, close inside the aperture for the 9th and 

 10th nerves ; these are the ex-occipitals {e.o., IX., X.). 



The next are formed in membrane, outside the ciirtilage ; they are the fronto- 



