DEVELOPMENT OF THE SKULL IN THE BATRACHTA. 71 



Already the passages for the 5th and 7th, and the 9th and 10th nerves (V., VII., 

 IX., X.) are being enclosed in bone. 



The trabeculfe and " intertrabecula " form the whole skull from the notochord to the 

 upper labials, the hinder half being cranial and the fore hoM nasal. 



The fontanelle {fo.) is not large, and it appears of a pyi'iform shape, because of the 

 fronto-parietals (/j).) which partly cover it ; they are strong wedges of bone close 

 together behind, where they are broad, and wide apart in front, where they are narrow. 



There is an enlargement of each bone in the temporal region, and from thence the 

 vincovered skull rapidly widens into the auditory masses. 



In front of that point it is almost oblong, only gently widening towards the front, 

 where it is continuous with the large facial bars. 



Tlie floor is flat — scarcely convex — and above the edge of the floor the sides are 

 scooped, and shelve inwards, so that the flat top is narrow, especially in front, where 

 the " tegmen" {t.cr.) reappears. 



The tegmen is continued in front of the closed cranial cavity, whose only fore outlet 

 is through the olfactory foramina (I.) ; therefore between these holes there is a part 

 answering to the " perpendicular ethmoid" {p.e.). This is continued forwards as a 

 crest growing up from the line of junction of the trabeculae ; it is the " septum nasi " 

 or fore part of the intertrabecula. Beyond this wall, with a slight interruption, the 

 trabeculas are united for a space, and then are free, and diverge at their end. 



These " cornua " are convex above and concave below, with a thick outer and 

 front edge (Plate 2, figs. 1, 2, c.tr.) ; and this part, ending in a flat facet, articulates 

 with a like facet on the upper labial (»./.). 



The coalesced part of each cornu is somewhat constricted, and a similar lunate 

 outline exists in the bar outside. Thus the inner nostril {i.n.) is made ; it is finished 

 in front by the short j;re-paZa<tnc ligament {pr.pa.), both cartilages approximating. 



Nearly the middle third of each trabecula is continuous with the outer band ; this 

 is in the ethmoidal region, which is very extensive. 



There are in reality two bands — one outer very large, and a smaller band lying 

 between this and the trabecula ; this lesser part is the " post-palatine" {pt.pa), and 

 the huge bar outside is the suspensorium of the loweV jaw {ppf/-, sp.). 



The inner bar is half the length and one-third the width of the outer ; its 

 hinder third is free, projecting backwards and hooked a little outwards between the 

 trabecula and the suspensorium. 



Its fore part is continuous with the inner edge of the suspensorium, whore it 

 bounds the inner nostril (i.n.), and ends in the inturned pre-palatine spike. The 

 middle part, which is the longest, is the conjugational tract binding together the two 

 main cartilages, outer and inner {c.tr., sp.). 



The upper part of the ethmo-palatine is strongly crested on its inner side, and this 

 crest meets tlie lateral ethmoidal wall at an acute angle behind the inner nostril 

 (Plate 2, fig. 1, p.2jg., »•«.)• 



