DEVELOPMENT OF THE SKULL IN THE BATRACHIA. G7 



little. The narrow part opens out elegantly into the ethmoidal wings ; up to them 

 the girdal-bone {etli.) reaches, and n(j further. Above, this bone reaches half way to 

 the extended prootic tract; below, two-fifths of the walls are soft, and this unossified 

 tract has in its middle a very large optic fenestra (II.). and l)ehiiKl, it encloses most of 

 the foramen ovale (V.). 



The nasal region is quite unlike that of a typical Frog; above (fig. 1), the nasal 

 roofs are very narrow, and merely form a crescentic selvedge to the septum nasi (s.n.), 

 and on to the fore margin of the ethmo-palatine band. 



The narrow roof curls round the front of the outer nostrils (t'.».), which are very 

 near each other — only one-third the distance apart tliat we have just seen in the Frog 

 from Lagos (Plate 13, fig. 7, e.n.); behind the opening the nasal wall {n.iv.) is thick 

 and crescentic. 



This narrowing of the nasal end of the skull is made more remarkable by the 

 development of a very distinct and pointed prenasal cartilage (j).n.).'"' 



But below (fig. 2, s.n.I.), the trabeculte have united to form a very wide elegantly 

 winged tract, which passes between the laminae of the maxillaries [mx.), externally : 

 behind, it is narro\\'ed, for each margin is cut away by a semi-circular notch, through 

 which the ijiternal nostrils {i.n.) pass. The " pro-rhinals " (p.rh.) are very long, 

 slender, and bent back upon themselves. 



These pi-ocesses (Plate 15, fig. 5, p.rh.) are impacted betwecm the two laminaj of the 

 premaxillary ; they are equal to the prenasal in thickness. 



The nasal valves (»./-.) are outside the nostrils ; they are, in foini, quite normal, but 

 very small. 



The whole of the palato-suspensorial arch is quite normal, and rather slender ; the 

 same is true of the bony plates (/^o., pg.). 



The pedicles {pd.) are wide apart, for the auditory masses are relatively large, and 

 widely outspread. The condyles of the quackate {q.c.) are a little further back than in 

 the last, are opposite the end of the stapes, and are large and reniform ; there is no 

 grafting of the quadrate -jugal over them. 



The Eustachian openings (fig. 2, ex.) are very large and are turned obliquely 

 backwards, outside ; the annulus is very large, and like that of the Bull-frogs (Eastern 

 and Western). The stapes (fig. 4, st.) is large and like that of the " norma ;" the 

 columella is very generalised ; there is no inter-stapedial segment at the scooped top of 

 the club-shaped medio-stapedial (in.st.) whose interstapedial end {i.st.) is not ossified. 

 By a short stem, the bony tract is connected, in front, with a small extra-stapedial {e..^t.), 

 which has no secondary process ; here, the breadth of the " annulus," below, is more 

 than twice as great as that of the circular extra-stapedial : this is the converse of what 

 is seen in Rana KuhU and DactijJethra. 



The investing bones are about as strong as those of tlie skull of "the type," when 



• The right dotted line from i^n. in fig. 1 points to the nasal process of the right premaxillary ; heliiiid 

 its apex the first upper labial is hidden. 



K 2 



