MR, W. K. PARKER ON THE STRUCTURE AND 
192 
The roofs ( cil.n.) are narrow crescents and only form a tract half the width of the 
floor (fig. 2); the septum (s.n.) is thick, and ends as a blunt mass, not projecting; the 
pro-rhinals (fig. 2, p.rh.) are rather small and inturned; the angles of the original 
cornua pass well into the maxillaries (fig. 2, mx.). 
From the upper surface of these angular growths a thick and widish crescent of 
cartilage grows up as a limited nasal wall (figs. 1, 3), behind the nostril (e.n.), and 
confluent with the roof (cil.n.). 
The two pairs of labials (u.U.u.l 2 .) that defend the nostril in front, are rather small. 
The palato-suspensorial arch is normal but very strong, and the usual bony plates, 
namely, the falcate palatine ( pa.) and the triradiate pterygoid {pg.), are normal, and 
leave an average amount of cartilage untouched. But the condyles of the pedicle and 
the quadrate { pci., q.c.) are very large and solid, and the latter region is partly ossified. 
The cartilage is left uncovered towards the end of the pedicle, which is not only 
very solid, but is also almost external in position. Moreover, the pterygoid bone forms 
a right angle by its fork, and in the space thus half enclosed there is an extremely 
large, circular Eustachian opening {eu.), whose boundary is finished by the hind process 
of the pterygoid, by the stylo-hyal, and by the binding web of fibrous tissue tying 
these together. 
The mandible (fig. 3) is normal: the dentary (d.) is half the length of the ramus ; the 
mento-Meckelian (m.mJc.) is large, and the coronoid process (ar.) low. The annulus 
(< a.ty.) is relatively almost as large as in Rana pipiens (Plate 8, fig. t), but it is widely 
open above (fig. 3); yet the drum, altogether, is large and well specialised, and its 
additional structures are nearly typical. 
The stapes (figs. 4, 5, 6, st.) is oblique, truncate, and lobate; it is gently convex 
externally, and gently concave within. 
The columella lias a reniform proximal osseous centre, which hardens most of the 
dilated upper end; this is the inter-stapedial (i.st.) ; it is segmented from the long 
medio-stapedial rod ( m.st.) by separate ossification, and not by separation of the 
primary cartilage. The distal cartilage is as long as the bony part {m.st.); the extra- 
stapedial (e.st.) is a compressed tongue, which gives off a ligulate supra-stapedial (s.st.) 
that is confluent with the ear-mass above. So also is the stylo-hyal (st.h.) confluent 
above ; it becomes first broader, and then narrower again as it passes round, without 
lobulation, to become liypo-hyal (see Plate 15, fig. 8, c.liy., h.hy.). 
The body (b.li.br.) of the basal tract is only two-thirds the extent of the notch in 
front ; it has no anterior lobe, and the posterior lateral lobe is long, pointed, and 
diverging. The bony thyro-hyals ( t.liy.) are normal, but in front of them the basal 
plate is occupied in its centre by a large basi-branchial endostosis (lj.br.). Also on each 
hypo-hyal there is a small oval extra-hyal piece ( e.liy.). 
The investing bones are normal as to strength, but they differ very much in certain 
regions from the norma : the fronto-parietals (j-p) cover two-thirds of the inter- 
auditory region, the right overlapping the left. 
