iv INTRODUCTION. 



wardly from Lake Superior to Lake Winnipeg and Western Canada, which fades 

 insensibly into the great Arctic district; 2, a middle province, limited westwardly 

 by the Appalachian chain, and extending to Southern Virginia; 3, a western pro- 

 vince, including Minnesota and the States of the valley of the Mississippi, as far 

 as the State of that name; 4, a southern province, including the States south of 

 Virginia and Kentucky; 5, a subtropical province, including the point of the penin- 

 sula of Florida; 6, a subtropical province, including the sea-coast of Texas. 



The Central district, as far as known, may be thus divided : 1, a northern pro- 

 vince, comprising the regions north of the Missouri, the plains of the Saskatchewan, 

 etc. ; 2, a middle eastern province, divided into two subprovinces, including : a, 

 Kansas, and Nebraska; b, northeastern New Mexico; 3, a southeastern province, 

 including Texas, with the exception of province six of the Atlantic district ; 4, a 

 southwestern province, including the upper part of the valley of the Gila ; and 5, 

 a south-southwestern province, including the lower Gila and Colorado. The unex- 

 plored portions of this district will indicate middle western, arid northwestern 

 provinces, or perhaps the necessity of constituting with them and the southwestern 

 province a district to be called the Interior district. 



The Pacific district may be divided as follows : 1, a hyperborean province, con 

 sisting of Sitka and the neighborhood ; 2, a northern province, including Eastern 

 Oregon and Washington Territories ; 3, a middle province, including California, 

 probably as far south as Santa Barbara; 4, a southern province, including Cali- 

 fornia from Santa Barbara to San Diego, extending to the crest of the Sierra. 

 Southern, or lower California is also, perhaps only in part, a province of this dis- 

 trict; 1 but, as yet, no collections of magnitude have been received therefrom. 

 Other provinces will, from the peculiar method of distribution of species in that 

 portion of America, be defined when more full collections are made, but at present 

 cannot be indicated. 



At the north, the Atlantic and Central districts seem to merge imperceptibly 

 together, about the valley of the Athabasca, and Winnepeg rivers, and finally to 

 disappear in the limited Arctic fauna ; the hyperborean province of the Pacific 

 district also fades into this Arctic fauna, without, however, losing itself so perfectly 

 in the northern provinces of the other districts. We have thus evidence that the 

 American Arctic district may be divided into two provinces, an eastern and a 

 western. 



At the south, the Atlantic district merges through Florida into the Caribbean 

 tropical province, and through maritime Texas into the Mexican lower eastern 

 province. In the same direction the Central district merges into the Mexican 

 upper or central province, and the Interior district, towards the Gulf of California, 

 into the Mexican western province. Regarding the southern affiliations of the 

 Pacific district we know absolutely nothing; scarcely a single species found at 

 San Diego has been found in Mexico. 



1 A few species, collected by John Xantus, Esq., at Cape San Lucas, though all new, indicate a 

 greater resemblance to the fauna of the lower Colorado, than to that of maritime California; this pro- 

 vince may therefore be found eventually to belong to the interior district. 



