90 MR. W. K. PARKER ON THE STRUCTURE AND 



shine through tlie thin walls of the sac, which is a small spheroid, growing into a free 

 edge on the outside, above. That "eave" of cartilage is the tegmen tympani {t.ti/.), 

 behind, and the confluent spiracular cartilage {sjj.c), in front; this ear-shaped flap just 

 touches the round elbow of the suspensoriuin — its otic region (pt.p.). The infero- 

 lateral face of the capsule is splitting to form the "fenestra ovalis" (f.o.), but the 

 stapes is not yet formed. Contrary to what was seen in the last two kinds, the inter- 

 orbital or fore half nf the cranium proper enlarges from behind forwards; it also 

 bultres a little at the sides. 



There are scarcely any "ethmoidal wings" {(d.c.) for the post-palatine rudiment 

 {pt.pa.) lies close to the skull, and the pterygo-palatine band {j)-2>9-) is very short ; it 

 turns forwards and outwards, and is surmounted by tlie thick, oblong post-palatine. 

 In front of the internal nostrils ('./'•) the trabeculse {c.tr.) do not grow towards the 

 prae-palatine rudiment {pr.pa.) as in the last two kinds ; they only, there, suddenly 

 become wider. The sides of the ethmoid (al.e.) can be seen to be older than the 

 tegmen (fig. 1, tr.) between and over them, and this latter part covers the rudi- 

 mentary " mesethmoid." 



The gently diverging cornua (c.<r.) increase a little in size up to their fore end ; but 

 they do more than this, they are convex above, turn gently downwards, and at their 

 outer edge curl over ; this fold thickens up to the end, where it is very solid ; it there 

 articulates with both the upper labials of that side [u.V'.u.V'.) ; this is very similar to 

 what is seen in Paeudis (Plates 2 and 11), where the upper labials are not divided. 



The falcate hinder part of the suspensorium (sp.) unites by its hooked end {pd.) 

 with the basis cranii, and this " pedicle " passes in between the orbito-nasal and 

 vidian nerves (V., VI I'.). The sub- oval condyle for the cerato-hyal [hij.f.) is inferior, 

 and projects from the root of the large oi'bitar process (or.p.) which nearly touches the 

 skull-wall ; it is only separated by a thinnish tract of fibrous tissue. Its ribbed edge 

 is decurrent along the suspensorium, fore and aft, reaching nearly to the condyle 

 (q., q.c.) and nearly to the ear. The pre-palatine rudiment [pr.pa.) is an upturned " ear " 

 of cartilage, giving attachment to the ligament that bounds the inner nostril in front. 



The quadrate condyle {q.c) is saddle-shaped, and looks somewhat inwards, as well as 

 forwards and downwards ; it has a round knob of the suspensorium outside it. The 

 upper labials {u.V'.u.V'.) are formed (as cartilages) separately; the inner pair are sub- 

 crescentic, the outer pedate, — the "toe" being the postero-extei'nal angle. 



The mandibles and lower labials (fig. 3, mk., l.l.) are of the same form as in Pseudis ; 

 they are short, massive, and obliquely articulated together. 



The other inferior arches (fig. 4) have their own characters. 



The cerato-hyal {c.hy.) is remarkable for the hollowing out of its upper part, which 

 is a curved shell of cartilage ; the condyle {hi/.c.) is oval, and there is a spike in front 

 of it. The basi-hyal {h.hij.) is composed of simple cartilage, the basi-branchial {h.hr.) 

 of hyaline, and it has a budding second joint. The large hypo-branchials {Ii.hr.) 

 are wide in front, and gradually narrower behind, where they are notched. 



