DESCRIPTION OF SPECIES EXAMINED 135 



two show true papillary ridges, viz., Didelphys azarce (Azara's 

 Opossum), and Trichosurus vulpecula. Petrogale penicillata (the 

 Brush-tailed Wallaby), Figs. 66 to 72, is interesting as showing 

 much higher development both of the epidermic nodules or 

 warts, and the papillse of the corium on the hind foot than on 

 the forefoot, and this is obviously correlated wnth the much 

 greater importance to this animal of the functions of the former. 

 Fig. 70 is instructive as showing the structure of the skin of 

 the heel, in wliich no nodules are seen on the surface, the outer 

 layer being much hardened, with entire absence of papillae 

 of the corium. 



The Edentate examined shows a low organisation of the 

 epidermis with flat scales, but a relatively high degree of 

 development of the papillse of the corium. Most of the eleven 

 species of Rodents have all the skin-structures poorly developed, 

 e.g., Arctomijs marmotta, the Alpine Marmot (Fig. 82) ; Xerus 

 cafensis (Fig. 81) ; H ystrix cristatus (Fig. 85) ; Erethizondorsatus 

 (Fig. 86) ; Myopotamiis coypu (Fig. 84) ; Ccelogenys paca 

 (Fig. 87). 



One of the most singular of these epidermic modifications 

 is that seen in Fig. 89, where a portion of the skin of the foot 

 of a common rabbit is shown. The long, closely-set hairs 

 are mixed with and attached to long rod-Uke extensions of 

 the epidermis, and possess thus very good examples of " tactile 

 hairs " ; the papillse of the corium are not here very highly 

 developed. The eighteen species of Carnivores examined are 

 \vith few^ exceptions {e.g., Arctigolidia trivergata, Fig. 93 ; 

 Viverra civetta, Fig. 95 ; Herpestes griseus, Figs. 96, 97 ; and 

 Proteles cristatus, Fig. 100), notable for the acuteness of angle 

 and closeness of the papillse of the corium, e.g., Felis doniestica 

 Figs, 91, 92, Suricata tetradactyla. Fig. 98; Canis familiaris, 

 Figs. 101, 102 ; Ursus Americanus, Fig. 103 ; Cercoleptes 

 (xmdivolvulus,F'ig. 105, and Lutra vulgaris. Fig. 106; MeUivora, 

 Fig. 107 ; the Mustelida-, Figs. 108, 109, 110. The general 

 differences between the differentiation of the skin-structures 

 of the Rodents and Carnivores is consistent wnth the greater 

 cerebral organisation and activity of habits of the latter group. 



