1878.] Development of the Skull in the Lacertilia. 215 



" songsters," these curious specializations reappear, but the parts are 

 lessened and modified. 



Even many of those metamorphoses of the skull, which when I 

 worked out that of the chick seemed to me to be peculiarly avian, and 

 indeed not to be found amongst the almost reptilian Ratitse, now 

 turn out to be lacertian also. 



For instance, the separate cartilages that pad the " basi-pterygoid 

 processes " of the skull and the pterygoid bones, at their articulation, 

 these appear in the lizard ; and even the division of the septum nasi 

 from the ethmoidal wall begins in Lacerta, and other lizards. 



That separation of the two regions has its explanation in the higher 

 birds, whose fore face hinges on the skull ; notably in the parrot. 



In Lacerta it is a mere " fenestra/' of no use to the creature ; so it 

 is in the semi-struthious Tinamou, and in some low, Southern passe- 

 rine birds, e.g., Grallaria squamigera. 



But in the huge Ratitae it is as absent, as in the Chelonia, and 

 the low chamasleon. 



This latter kind has no column-shaped bone on the pterygoid (" epi- 

 pterygoid") ; that bone exists but is small and modified in the Che- 

 lonia; in birds, especially the "songsters ," it is manifestly & process of 

 the pterygoid, but I have never seen it as a distinct bone. 



These are some of the more striking characters in the skull of the 

 adult lizard and its sauropsidan relatives, namely, snakes, tortoises, 

 crocodiles, and birds : the latter, it may be remarked, differ less in 

 their structure from a lizard than many an imago-insect does from its 

 pupa. 



I have a strong suspicion that the serpent is degraded as well as 

 more ancient and generalized, as compared to the lizard : it has mani- 

 festly lost its limbs, and the correlate of that loss is an arrest of 

 the cartilaginous cranium. The small rudiments of orbitosphenoids 

 and alisphenoids, seen in the snake, are no longer an anomaly and 

 unexplainable : they are patches of the large tracts in the lizard, which 

 has, contrary to what I long believed, a large alisphenoid on each side. 



This part is not a continuous flap of cartilage : in the bird it is, but 

 it always has a great fenestra in its middle, even in them ; in the 

 lizard it is multi-fenestrate — a mere basket-work of cartilage, feebly 

 and partially ossified. 



In its auditory structures the high Lacertian corresponds very 

 closely with the tortoise and the crocodile, and these three kinds differ 

 only in non-essentials from the bird. 



The snake and the chamasleon lie below them all, but the chamaaleon 

 is lower than the snake, and has a worse ear than most frogs and 

 toads. The lower jaw of the lizard and the nestling bird agree very 

 closely. The remains of the hyoid and branchial arches are far more 

 ichthyic in the lizard than in the bird. 



Q2 



