106 



otrigonate type of dentition prevailed to a great extent in the older 

 forms of the order, and as those forms are now characteristic of those 

 regions in which generalized types exist in the greatest number, the 

 monotrigonate Insectivores may provisionally be tenants of that rank. 

 Future discoveries in palaeontology and individual development may 

 throw light on the subject. 



GEOGEAPHICAL EELATIONS OF AMERICAN SPECIES. 



Prepared from the standpoint thus obtained to inquire into the rela* 

 tions and distribution of those types represented by American species, 

 the conclusions may be generalized as follows : 



The North American species now living belong exclusively to groups 

 confined to those quarters of the world in which have become developed 

 the most differentiated types ; that is, the great " Arctogfean" division. 

 No forms clearly susceptible of more than "group" distinction from 

 types characteristic of the Pal^arctic province of that division exists 

 -within its limits. More detailed study gives thefollowing results : In the 

 family Talpidw are several peculiar genera, representing even somewhat 

 more comprehensive groups : thus, in the subfamily Talpince are two well 

 differentiated groups : — (1) Scalopes, with two genera ; and (2) Gondylura'^ 

 with one genus ; while the Ta/^xi' of the Old World are otherwise unrepre- 

 sented in the new. The Myogalinoe, on the other hand, are represented 

 by a genus ( Urotrichus) whose typical representive is a Japanese animal, 

 and from which, indeed, the Western American species seems to be 

 scarcely distinguishable. 



The Soricidw are represented by genera either common to the nearc- 

 tic and palnearctic faunas, or by extremely closely related ones. 



In fine, the affinities existing between the Northern Old- World and 

 New-World forms are such as to render it evident that whatever may 

 be the origin of one, that, directly or indirectly, must be the source of 

 derivation for the other. As the fauna of South America and the West 

 Indies is exceptional, it is out of the question that the original center 

 is there ; and palieontological and physical geography, re-enforced by 

 zoological geography, concur in pointing to the jn^obability that to 

 Asia we have to look for at least the secondary source of emigration of 

 the arctogfean forms. 



Without further preface, the contrasted differential characters of the 

 various groups of the order are given, and their successive degrees of 

 subordination exhibited in the following analysis : 



INSECTIYOPvA. 



Ineducabilian Placental Mammals,* with the anterior as well as poste- 

 rior members primarily adapted for walking! (but secondarily modified 

 for other i)urposes), the carpal bones of the proximal as well as distal 

 series, and the metacarpal as well as phalangeal bones being normally 

 differentiated and developed ; the ulna and radius more or less dis- 

 tinct ; the hind limbs normally related to the pelvis, and their elements 



* Ineducabilian Placental Mammals, i. e., Placentiferous Mammals with a brain whose cere- 

 brum is relatively small and unilobate, (the sylvian fissure beings obsolete and the posterior 

 lobe undeveloped, ) leaving exposed behind much of the cerebellum and in front much of the 

 olfactory lobes, and with the corpus callosuur extending more or less obliquely upwards, 

 terminating before the vertical of the bippocampal sulcus, and provided with no well-de- 

 fined rostrum in front. 



t In contradistinction to the Cheiroptera, which have the manus primarily adapted for flying 



i 



