INSECTIVORA OF THE SANTA CRUZ BEDS. 381 







adaptation to similar habits of life than to genetic relationship. The 

 more the Santa Cruzian fauna is studied, the more clearly does it appear 

 that these southern mammals are but very remotely connected with their 

 analogues of the Northern Hemisphere. Rutimeyer's suggestion of a 

 southern centre of origin and distribution becomes, with advancing knowl- 

 edge, distinctly more probable than the view which regards all southern 

 types as having migrated from the great northern centres of development. 

 Another important corollary of the reference of Necrolestes to the 

 Chrysochloridce is that it makes necessary, or at least probable, the assump- 

 tion of a land connection between Africa and South America. There is 

 no reason to suppose that the track 'of migration could have been by way 

 of Europe and North America, for no trace of this family has ever been 

 found in any of the northern continents. This supposed connection of 

 Africa with South America has often been suggested before and is sup- 

 ported by many independent lines of evidence. Into the discussion of this 

 evidence it is not necessary to enter here, for it has lately been summed up 

 by Lydekker ('96, 127, 255) and Tullberg ('99, 491) and must again be 

 considered in the general statements concerning the Santa Cruz fauna as a 

 whole. It may be pointed out, however, that the presence of Necrolestes in 

 Patagonia is, so far as it goes, distinctly confirmatory of the hypothesis. 



NECROLESTES PATAGONENSIS Ameghino. 



(Plate LXIV, figs. 1-5.) 



Necrolestes patagonensis Amegh. ; Rev. Argent, de Hist. Nat., T. I, 1891, 



P- 303- 



Though I have referred all the specimens in the collection to this spe- 

 cies, it is not altogether improbable that more than one species is repre- 

 sented among them. The type of N. patagonensis is a left mandibular 

 ramus, lacking the coronoid and symphysial region. As already men- 

 tioned, this individual is remarkable for the great size of the canine root, 

 which is plainly divided into two, and rises so high above the alveolus as 

 to raise the base of the crown above the tops of the grinding teeth. In 

 the Princeton specimens the enamel-covered crown of the tooth descends 

 into the alveolus, the root is much smaller, though there is some individual 

 variation in this respect, and I cannot detect any division of it. If the 

 peculiarities of the type are normal and not pathological, it will probably 

 prove to be specifically distinct from the Princeton specimens. 



