DEVELOPMENT OF THE SKULL IN THE BATRACHIA. 119 



liind part of the septum nasi (s.n.), and tlie hiding of the outer part of the bone by the 

 vomers (see figs. 6 and 9). Contrary to rule, the upper and lower outlines of the nasal 

 region are veiy similar. 



Above, a large and shallow, and, below, a narrow and deep, notch on each side, shows 

 where the ethmoidal territory ends and the nasal begins, and these emarginations show 

 that the nasal region is short ; the thickness of the convex roof hides the form of the 

 dividing septum nasi. Below (figs. 6 and 9), the girdle- bone ends in a sinuously- 

 rounded margin, a short distance behind the notches in the sides. The bone is sinuous 

 on its surface, first scooped in the middle, then swollen on each side, a groove sub- 

 transversely dividing these swellings from the " wings." In front of the notches, the 

 subnasal lamino3 (fore part of trabecular cornua, s.n.l.) are ossified, each bone taking up 

 one-third of the floor. A bone half the size of these has been formed in the cartilage 

 of the median tract ; it reaches from the nerve-passages {n.n.) to the decurved rostrum 

 ip.n.). These three bones, like the ethmoid or " girdle," being ossifications of the 

 three basi-cranial bars — like those found in so many types in the region of the brain 

 cavity — may be entitled to the name of "serial homologues" of such segment-forming 

 bony centres." 



The lateral subnasal ossifications are rugged and prickly at their marguis ; their 

 middle is somewhat elevated, transversely; the " pro-rhinal process" of the cartila- 

 ginous matrix [p.rh.) is small. 



The upper surface, formed mainly {i.e., except at the middle line) by the nasal roof- 

 cartilages (fig. 7, al.n.) is broad, gently convex, and passes insensibly into the prenasal 

 rostum (figs. b-7,p.n.). 



The suborbital space {f.p. to pg.) is large and sub-oval ; its outer fence is the palato- 

 suspensorial arch. The ethmo-palatine bar, like the rest of the cartilaginous pith of 

 this arch, is slender, and runs outwards and forwards, like a continuation of the wing 

 of the ethmoid ; it is bi-aculeate in front (fig. 9, e.pa.). The post-palatine portion 

 (behind e.pa.) can be seen to be but little affected by the palatine bone (fig. 6), which 

 is a normal sub-falcate blade, separated by almost its own length from its fellow, and 

 not reaching the pre-palatine spm- in front. But the pterygoid {pfj.) either ossifies or 

 conceals much of the hinder part, yet the inner fork or pedicle (fig. 5, pel.), and the 

 tract leading to it in the edge of the folded pterygoid (fig. 7, pg., xp.) shows that the 

 axis is nowhere quite lost. But on the under surface (fig. 6, pd.) the pedicle is seen 

 to be tied down by the pterygoid bone so that all motion is lost, and this inner tongue 

 of the bone forms a strong squamous suture with the prootic and para.sphenoid ; this 

 is a Bufonine character, as we shall see. 



But the outer fork, or quadrate region, becomes much larger, and the part above the 

 condyle is largely ossified by the quadrato-jugal (figs. 6, 7, q., q.c, <].J.). 



• In Birds, ossifications of this kind in the precranial region of the base are very common ; but in tlieir 

 ■ compressed prognathous head the fore part of the intertrabecula is early absorbed ; the paired trabeculae 

 end behind the intertrabecula and the "subnasal laminai" arc only exceptionally developed. 



