252 BULLETIN OF THE 



chusetts that have not been detected in the latter. Two of them — 

 Didelphys virginiana Shaw, and Lepus glaciulis Leach, the former 

 occurring in Southern New York, and the other attributed to Northern 

 Maine, and known to occur in Newfoundland * — are not likely to occur 

 here. The other two, Sorex Thompsonii Baird f and Blarina augusti- 

 ceps Baird,$ — the latter described from a specimen taken at Burling- 

 ton, Vermont, and the other reported from the same locality, from 

 Halifax, N. S., and Maine,§ — are of a highly questionable character. 

 What has been called Sorex Thompsonii (the young probably of either 

 S. Forsteri or S. Cooperi) doubtless occurs here. 



looked, the argument is one-sided, only half the truth is reached, and the general view is 

 a distorted one. 1 



As I have already remarked above, the mutual resemblance between the faunae and 

 florae of the boreal portions of North America and those of the Europeo-Asiatic con- 

 tinent is exceedingly great, amounting in the arctic portion, as was long since pointed 

 out, 2 almost to identity. In the Arctic province, which occupies the woodless tracts in 

 the extreme north of both continents, more than four fifths of the species found on the 

 one continent occur on the other. While a few of the small number that inhabit this 

 region are restricted to it, the larger part range much farther to the southward, the 

 majority even over the colder part of the north temperate zone, and several throughout 

 this zone. Besides the mutual floral and faunal resemblance between the two northern 

 continents imparted by this wide distribution of the circuinpolar species, this resem- 

 blance is increased by the large number of genera that are circumpolar, besides those 

 that embrace the circumpolar species, and the occurrence of other forms, both specific 

 and generic, that are closely allied. It is also true that among the forms restricted to 

 each continent are a few family groups; yet the number of these, as of species and gen- 

 era, that occur in the tropical and not in the colder temperate regions on either continent 

 is far greater than that of those peculiar to either of the two northern continents. Con- 

 sequently to apply as ontologico-geographic designations such terms as " Palseogean 

 Creation" to the Eastern world and "Neogean Creation" to the Western, virtually im- 

 plies the ignoring of the real close affinity of the life of the whole northern hemisphere 

 at the northward, and the vast difference between that of the tropical and the cooler 

 north temperate regions on the same continent. But a further discussion of this point 

 is uncalled for now, and is, moreover, the more out of place here, since I shall, I trust, 

 soon have an opportunity to treat it in detail in a more legitimate connection. 



* Quad. N. Am., Vol. I, p. 248. t N. Am. Mam., p. 34. 



t Ibid., p. 47. 



$ Proc. Bost. Soc. Nat. Hist., Vol. IX, p. 169. 



i See Murray's Geog. Distrib. of Mammals ; Wallace's Malay Archipelago, etc. 

 2 See Agassiz's papers, cited above. 



Cambbidge, October, 1869. 



