1GO MAMMALIAN DESCENT. [LECT. VL 



small ; they are quite normal, and the stapes (stirrup) is 

 well shaped, with a large foot-hole ; the rest of the hyoid 

 arch is complete. The tympanic annulus, or ring-bone 

 of the ear-drum, is rather slender, but has a broad flange 

 on its hinder crus or limb ; there is only a low ridge on 

 the basi-sphenoid (skull-balk), helping to wall in the 

 cavum tympani, or drum cavity ; the concha or free 

 part of the ear is well developed. Thus we miss in this 

 diminutive type the cheek-bones (malars or jugals), and 

 the tympanic wings of the basi-sphenoid ; these parts 

 have gone in the general reduction of the type ; they 

 have become small by degrees, and beautifully less, 

 through the secular periods during which the Eutheria 

 have been struggling upwards. 



The ripe embryo, and the embryo when five-sixths 

 ripe, are like little generalised Pigs, but their snout is 

 obtuse, not discoidal, as in those rooting beasts. In their 

 general appearance both the embryos and the nestlings 

 might be taken as models for the restoration of the 

 forms whose skeletons are found in the Upper Eocene 

 deposits ; only in size do they come short ; some of those 

 lost types (Palceotherium, Anoplotherium) were cattle 

 of considerable dimensions. The probability is that the 

 Shrews have, on the whole, kept most of their original 

 characters as early Eutheria ; but that they have under- 

 gone, besides gradual lessening of bulk, gentle changes 

 of structure, in conformity with their habits. Their 

 safety during all this time has been due to the fact that 



