nKVELOPMEXT OF TTTK SKULL TX TTTR BATRACHTA. 109 



The pterygoid {pg.), on the other hand, has used np most of the cartilage to which 

 jt clings, and growing beyond the pith of the pedicle (pel.) makes this part pointed. 



On the right side, that independent ossification of the outer and inner elements 

 which is so common in the " Anura," shows itself in a remarkable manner, for the very 

 apex of the cartilage becomes detached, as a "meniscus," and then thoroughly ossified, as 

 a small, free, diamond-shaped " metapterygoid " (figs. 5 and 5a, ])d., pd.m.). In Rana 

 temporaria, and others of that genus, the metapterygoid, which appears during 

 metamorphosis, is formed in the outer fibrous layer : here it is endoskeletal. The 

 quadrate region is neither long, nor far retreated (fig. 2, q.c), it is all ossified by 

 the quadi'ato-jugal, except the apex of the otic process, which is continuous with 

 the slight remaining pith of the pterygoid, and the edge of the tegmen tympani 

 (fig. 5, .sjj,, q., pg.c, pr.o.). The condyle {qc.) which ends opposite the middle of the 

 stapes (st.) is a large, well-formed trochlea, strongly clamped on its inner side by the 

 pterygoid. That process forms a very obtuse angle with the pedicle, and here a very 

 small crescentic slit can be seen just through the skin of the mouth, its convex side 

 lying against the bone : this is the blind Eustachian opening (ew.). Outside the 

 suspensorium a very small annulus (figs. 3 and 6, a.ti/., m.ty.) is seen ; it forms three- 

 fourths of a cu-cle, its diameter, and the breadth of the band, is about one-third 

 that of a typical Frog. 



The mandible (fig. 3) is very strong, especially in its hinder part ; it is, however, 

 quite normal. 



The stapes (fig. 6, st.) is of the average size ; it is a very regular oval, but has a 

 rounded process behind, and an oval " boss " outside. 



The columella is extremely delicate, and is not segmented. The medio stapedial 

 lione (m.st.) occupies the dilated stapedial end, and runs along the thread of cartilage 

 so as to be one-third the length of the whole rod, which ends as an ai'cuate extra- 

 stapedial (e.st.) ; this is spatulate, and without a fork. 



The stylo-hyal (fig. 2, s.th.) is confluent with a trace of cartilage on the outside of 

 the floor of the vestibule ; it enlarges in its de.scent (fig. 4, c.hy.), and becomes partly 

 ossified. There is a small, sharp hypo-hyal lobe (h.hy.) in front, and one on the side ol" 

 the short retral part ; between these bars the " notch " is a very large crescent. 



For the ba-sal plate is very wide and short, and is of the same kind as we see in 

 Calyptoceplmlus (Plate 21, fig. 4) — a near relative. There is an adze-shaped fore, and a 

 styliform hind, lobe on each side; the thyro-hyals [t.luj.) are large, dilated, and separated 

 by a space which is two-thirds of a regular oval. The proximal part of these bars take 

 up half the ba.sal plate, and they almost meet at the mid-line. The rest, all but the 

 front edge and part of the fore-lobes, is semi-osseous. 



Like some other sub-typical Frogs — Pleurodema, Lymitodynastes — the fronto- 

 parietals [f.p.) do not finish the roof but are scanted in their front half, and end as 

 rounded bars, each one-third the breadth of the roof Behind, they are strong, 

 smooth, sinuous, falling in at the temples, and swelling over the anterior canals, and 



