26 PSYCHE [April 



The idea underlying it is this : — a combination of zonal and topographical 

 features in a diagram in such manner as to present both the zonal and the approxi- 

 mate geographic distribution of the fauna or flora of a given territory, either past 

 or present, in a graphic way, thereby facilitating the study of both kinds of 

 distribution and the tabulation of results. Diagrams will differ according to the 

 factors involved, — life-zones, societies, etc., on the one hand, and topographic 

 regions, features, etc., on the other, but the plan is capable of wide application. 

 The diagram here shown is designed with especial reference to the United States 

 and Canada. 



The seven life-zones (following Merriam) are arranged in a vertical series 

 beginning with the Tropical at the bottom and ascending through the Lower and 

 Upper Austral, Transition, Canadian, and Hudsonian, to the Arctic-Alpine. The 

 meridional extent of the country is divided into an east and west series of regions, 

 ten in number, based on the more salient features of topography, and named, 

 beginning with the easternmost: — Atlantic, Appalachian, East Central, West 

 Central, Plains, Cordilleran, Basin, Sierran, Californian, and Pacific. Each wider 

 region is represented in the diagram by a column made up of a square area in each 

 zone ; each narrower region by a narrower column one-half or two-thirds as wide 

 as the former. The tropical zone, being restricted to areas of inconsiderable size 

 in three widely separated regions, — Florida, Texas, and Arizona, — is represented 

 by small squares attached to the Lower Austral zone at the proper points. Sub- 

 divisions are indicated in the case of the Gulf strip and Austro-riparian sections of 

 the Lower Austral, and the arid western and humid eastern divisions are separated 

 by a double line. 



But little attention relatively has been paid to the zonal distribution of 

 particular groups of insects over a broad extent of country and there is a wide field 

 for records in this line. Desiring to test the practical working and value of this 

 scheme in relation to a group of animals whose zonal distribution has been care- 

 fully studied, I have applied it, at the suggestion of Mr. Glover M. Allen of the 

 Boston Society of Natural History, to the genus Neotoma^ using for comparison a 

 series of tinted maps, with excellent results. 



In practical use the diagram is treated like the outline map, a copy being used 

 for each species or variety, and the presence of a species in a given zonal area is 

 indicated by a cross, dash, or other convenient and rapidly made mark (or tint if 

 preferred), the totality of these marks indicating the zonal distribution and the 

 approxitnate geographical position as xvelL This graphic element is believtid to be 

 a most valuable feature of this scheme, aiding greatly in the preparation of the 



' See Dr. Merriam's paper in Proc. acad. nat. sci. Pliiln.. 1894. 



