8 REVISION OF AMERICAN MOLES— TRUE. 



within the faunal areas outlined by students of zoo- geography, from 

 the investigation of other groups, whether their present distribution is 

 fortuitous, or dependent on ascertained or ascertainable conditions of 

 the environment, and what renders tliese conditions of importance, 

 are among the questions which deserve consideration. 



We have in North America, as already intimated, five genera of moles, 

 Scalops, ScajHinuSj Farascalopa, Gondylura^ and J^eurotrichus. Two of 

 these, namely, Scapanus and Weiirotrichus, are Pacific Coast genera. 

 Though the two genera are not closely related, their distributional 

 areas coincide, but Xciirotrichus, so far as known, extends by no means 

 so far south as Scajjantts. 



East of the Rocky Mountains are the three remaining genera, Scalops, 

 Gondylura, and Parascalops. The last two, as in the case of the west 

 coast genera, coincide in distribution to the extent that Parain'fdopH 

 occurs over the middle and southern portions of the area occupied by 

 Condylura, and not elsewhere. But, so far as known, it does not range 

 nearly so far north or west. Finally, Sealops has a range much exceed- 

 ing that of the other two genera, with boundaries coinciding for no 

 considerable distance in any direction. 



Thus, while two or even three genera of moles will be found in a 

 single locality, no two are found everywhere together. Though the east 

 or west boundaries of two genera may coincide, the north and south 

 boundaries fail to do so, or vice versa; or at least the area of the one 

 genus will be found to exceed that of the other in some direction. 



As already stated, such coincidences as do occur are not correlated 

 with nearness of relationship, a fact which finds many parallels in the 

 class of mammals generally. 



The two investigators who have given most attention to the study of 

 the geographical distribution of American mammals in recent years 

 are Dr. J. A. Allen and Dr. C. H. Merriam.' 



The systems of these two writers, based on the effects of climate, while 

 they lead in the main to similar results, proceed from somewhat difler- 

 ent principles, Dr. Merriam giving almost exclusive attention to tem- 

 perature effects and relegating the moisture to an entirely secondary 



indebted to Dr. C. Hart Merriam for the use of the very large collection made under 

 his direction for the United States Department of Agriculture and of valuable spec- 

 imens of Condylura, Parascalops, etc., from his ]>rivate collection ; to Dr. J. A. Allen, 

 for the use of the collection of the American Museum of Natural History, New 

 York ; and to Mr. S. N. Khoads, for opportunities to examine various interesting 

 specimens in his private collection and in the Academy of Natural Sciences, Phila- 

 delphia. To these naturalists, and to the authorities of the institutions mentioned, I 

 ofler my sincere thanks, remem1)ering their forbearance in allowing me to retain the 

 collections for a very consideral)le period of time. 



'J. A. Allen: The Geographical Distribution of North American Mammals. Bull. 

 Amer. Mus. Nat. Hist., IV, 1892, pp. 199-244. 



C. H. ISIerriam: North American Fauna, No. 3. The Geographical Distribution of 

 Life in North America. Proc. Hiol. Soc, Washington, YII, 1892, pp. 1-64. Laws of 

 Temperature Control of the Geographic Distribution of Terrestrial Animals and 

 Plants. Nat. Geog. Mag., VI, 1894, pp. 229-238, pis. 12-14. 



