Lect. III.] THE HARD PALATE. 75 



vomerine series of bones have behind them, under 

 the main skull, another series, namely, the "para- 

 ■sphenoid" and its divisions. This series, as I shall 

 afterwards show, appears in the Mammalia, and the 

 arrangement is always as one, two, or three — a recollec- 

 tion, so to speak, of the primary pattern of median and 

 sub-median l)ones in the lowest Ganoid Fishes. Tn the 

 mammals, generally, during the embryo stage, there 

 nre five vomers, but in Marsupials there may be ten. 



Character 2. — The bony palate is deficient in the 

 Hedgehog and other low Eutheria, and is very limited in 

 the lower Eodents. Such a specialisation of the cheek 

 and palate bones is only rudimentary in the Amphibia, 

 in Serpents, and in Lizards ; in the larger Chelonia 

 (Turtles) it is very considerable, while in the Crocodile, 

 as in some of the lowest Eutheria, e.g., Ant-eaters, it 

 attains its utmost development. In birds, which, more 

 than any other group, lie away from this line of descent, 

 this structure is very slightly developed. 



Character 3. — This character, the hollo wness of the 

 squamous part of the temporal bone, is very marked in 

 the lower Eutheria, such as Edentates and Insectivora. 

 In the tailed Amj^hibia there is no drum-ca^dty ; in the 

 tail-less kind, where it is generally present, I never saw 

 this cavity enlarged by extension of the air-cell into the 

 neighbouring bones. Nor in Serpents or Lizards is 

 there any excavation of the bones in this part ; the 

 former have no drum cavity, most of the latter have. 



