242 



SCIENCE. 



[N. S. Vol. I. No. 9. 



dry interior of British Columbia and the 

 plains of the Saskatchewan to Costa Rica. 

 The regions occupied respectively bj'' the two 

 groups, however, do not to any great ex- 

 text overlap, Thomomys occupying in the 

 United States the area west of the Great 

 Plains, and the Geomys group the region be- 

 tween the Mississippi River and the eastern 

 base of the Rocky Mountains, with outlying 

 representatives in northern Florida and the 

 contiguous portions of Alabama and Geor- 

 gia. In Mexico Thomomys ranges over the 

 peninsula of Lower California and a large 

 portion of the interior of Mexico, which lat- 

 ter region it shares with numerous forms of 

 the Geomys group, now broken up by Dr. 

 Merriam into no less than nine genera. 

 These collectively not only occupy a large 

 part of central and southern Mexico, but 

 extend as far southward as Costa Rica. 



In respect to material Dr. Merriam has 

 been especially fortunate, having availed 

 himself of opportunities at his disposal as 

 Chief of the Division of Ornithology and 

 Mammalogy of the United States Depart- 

 ment of Agriculture, to bring together ma- 

 terial from a wide area and in an abimd- 

 ance scarcely dreamed of by any previous 

 monographer of the group. Of the one 

 tboi^sand specimens thus rendered avail- 

 able for study, over two hundred are from 

 Mexico and Central America, from which 

 area the specimens previously handled by 

 investigators could be counted on the fin- 

 gers of the two hands. Hence not only has 

 the known area inhabited by these animals 

 been greatly extended, but the harvest of 

 specimens has yielded novelties not pre- 

 viously suspected to exist. 



Only about one-half of Dr. Merriam 's 

 excellent memoir is given to the systematic 

 descriptions of the genera and species, the 

 first hundred pages being devoted to the 

 generalities of the subject — habits, func- 

 tion and structure of the cheek pouches, 

 food, sexual and individual variation, geo- 



graphical distribution, etc., about 15 pages — 

 and to chapters on the morphology of the 

 skull (30 pages) and the dental armature 

 (36 pages). Nearly seventy of the text fig- 

 ures and six i^lates relate to the structure 

 of the skull and teeth, this profusion of 

 illustration greatlj^ facilitating a clear com- 

 prehension of the points discussed in the 

 text, and formtag a most important feature 

 of the work. 



In coloration, size and in external details 

 generally, the species of Geomjddje are very 

 much alike. There are, however, large 

 forms and small forms, between which there 

 is a wide difference in size, and also forms 

 that are normally plumbeous instead of the 

 usual shade of yellowish browTi, but in gen- 

 eral, even for the discrimination of species, 

 resort must be made to structural details of 

 the skull and teeth, which often afford char- 

 acters of importance where external differ- 

 ences are nearly inappreciable. The range 

 of variation in cranial and dental charac- 

 ters is so great, in these animals which 

 look so much alike externallj^, that Dr. 

 Merriam has felt justified in separating the 

 old genus Geomys into nine groups which he 

 thinks should rank as genera, ' several of 

 which ' he says, ' are of supergeneric value.' 

 These genera are Geomys, Pappogeomys, Or- 

 tJiogeomys, Cratogeomys, Platygeomys, Orthogeo- 

 mys, Heterogeomys, Macrogeomys and Gygogeo- 

 mys. While these are apparently natural 

 groups, doubtless taxonomers will differ as 

 to whether all are entitled to full generic 

 rank. 



In 1857 Baird recognized seven species of 

 Geomys, of which six retain place in Mer- 

 riam's list. In 1877 Coues, in his mono- 

 graphic revision of the genus, admitted five. 

 During the last two years others have beeu 

 described, raising the number currently 

 admitted in 1894 to sixteen. To this num- 

 ber Dr. Merriam here adds twenty-one, 

 raising the total of species and sub-species 

 to thirty- seven ! Only the genera Geomys 



