IGO MAMMALIAN DESCENT. [Lect. YI. 



small ; tliey 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 j)eriods 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 eml^ryos and the nestlings 

 might be taken as models for the restoration of the 

 forms whose skeletons are found in the UpjDer Eocene 

 dej)osits ; only in size do they come short ; some of those 

 lost ty23es {Palceotherimn, 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 



