198 
ME. W. K. PAEKEE ON THE STEUCTUEE AND 
almost entirely formed of membrane, and then afterwards of membrane bones. Where, 
as in Chelonians, and especially Lacertians, something more solid is early developed, it 
soon ossifies, and becomes curiously modified as the “ epipterygoidean columella.” Not 
only the Reptilian group, generally, but the Lacertilians themselves, vary in their facial 
structures much more than the so-called Bird-Class ; three of the “ Families” may suffice 
for illustration. In the “ Varanians” (e. g. Psammosaurus) the long outgrowth of the 
stapes is only differentiated from the top of the second postoral by stoppage of ossification, 
as in the Crocodile and Sphenodon ; its stapedius muscle sends its tendon through the two 
forks of the “ suprastapedial” to the end of the spatulate “ extrastapedial;” and the car- 
tilage sends down an “ infrastapedial” close in front of the stapedial shaft. The long, 
flexible stylo-hyal is free as in the newly metamorphosed Frog, and articulates with the 
cerato-fiyal below (Huxley and Hawkins, “Atlas,” pi. 8. fig. 15, b). Here the Ichthyic 
and Batrachian structures are but thinly veiled. 
In the Chameleons (C. vulgaris) the “ membrana tympani” is abortively developed; 
there is no “ fenestra rotunda,” and the stapedial connective articulates with the top of 
the second postoral, a joint-cavity intervening between it and the “ medio-stapedial” pro- 
cess. Nearly all the suprastapedial is reduced to membrane ; there is no distinction be- 
tween the extra- and the infrastapedial regions. 
In the Cyclodonts ( Cyclodus nigro-luteus , and Trachydosaurus rugosus ) there is a 
“fenestra rotunda;” but the “membrana tympani” is a mere band, as in Sphenodon. 
Here the unossified end of the stapedial shaft is bulbous, and is loosely attached to a 
feeble unossified “ hyo-mandibular,” which ends above in a very short, rounded “ supra- 
stapedial” process; a feeble aculeate “extrastapedial,” grows from its side, and it ends 
below in a bluntly styloid “ infrastapedial.” These types are introduced to illustrate 
what I have said of “ secondary connectives ;” in the Crocodile, Sphenodon , and Monitor 
the stapes passes into the hyoid pier just as the quadrate region of the second facial 
bar passes into the prefrontal region of the first in the Frog. 
In the Chameleon and Cyclodont the stapes sends forwards the “ connective,” which, 
however, does not pass into the hyoid, just like the pterygo-palatine connective of most of 
the Orders of the Fish-class. 
2. With the Skull and Face of Birds. — The parts under especial consideration are de- 
scribed by Professor Huxley in his above-cited paper (pp. 398, 399) ; but I cannot 
agree with one expression — namely, that the “ suprastapedial ” is represented only by 
fibrous tissue ; I would say principally . 
The broad bent end of the infrastapedial {op. cit. fig. 5, 1.S) is not unfrequently ossified, 
and much more developed than in the Fowl ; this bony centre is not segmented off, and 
yet it is evidently the stylo-hyal ; it is hatchet-shaped in Gymnorhina tibicen , spatulate in 
Fruticicola rubetra , and styloid in Sula alba. 
In my last paper (Philosophical Transactions, 1869, pp. 755-807, Plate lxxxi.-lxxxvii.) 
I have not worked out the relation of the stapes to the hyoid arch in the first stage. 
In the second (Plate lxxxi. figs 5 & 9) the stapedial plate is already continuous with the 
aborted hyoid pier : that rudiment has already three processes, the first appearance of the 
