4 BULLETIN: MUSEUM OF COMPAEATIVE ZOOLOGY. 



cerning my limitation of the Cape region, I will answer that for the 

 flora it seems best to include only the region south of a line between La 

 Paz and Todos Santos. This line is nearly a straight line, and follows 

 along the northern base of the Cape Mountains. The trail between La 

 Paz and Todos Santos does not appear to ascend more than 150 feet 

 above sea-level ai any place, and there is a large extent of nearly level 

 country to the north of it. The Cape Region will be, then, a mountainous 

 country separated from the northern mountains by an extent of low- 

 land." 



The depressed and exceedingly arid desert tract above mentioned 

 evidently forms nearly as complete a barrier to the northward and south- 

 ward extension of plant and animal life as would a similar expanse of 

 ocean. Indeed, there can be little doubt that the comparative isolation 

 which its presence affords to the region lying to the southward has had 

 very much to do with the stril^ing fauna! and floral characteristics of 

 the latter area. Another factor of perhaps almost equal potency is the 

 comparatively humid climate of the Cape Region with the resultant (but 

 also only comparative) luxuriance of its vegetation. 



The limitations so concisely yet clearly stated by Mr. Brandegee are 

 those which I have adopted in the present paper, but I have ventured 

 to construe these (wholly without his knowledge or sanction) as includ- 

 ing the island of Espiritu Santo, whose founa, judging by what little we 

 know of it, seems to be essentially similar to that of the region lyinc 

 about and to the southward of La Paz. 



It was my original intention to insert in this connection some general- 

 izations bearing on the characteristics and affinities of the fauna and 

 flora of the Cape Region, as well as to tabulate the names of its various 

 birds in lists of permanent residents, summer residents, winter residents, 

 migratory visitors, etc., but I have found so very many cases where all 

 the information at my command has proved insufficient to enable me to 

 reach definite conclusions, that I have become convinced that the time 

 has not as yet arrived when it is either safe or profitable to attempt any- 

 thing of the kind just indicated ; I may venture to say in passing, how- 

 ever, that, as Professor Baird pointed out in 1859, the characteristic 

 birds of the Cape Region appear to be more closely related to those of 

 Arizona and Northwestern Mexico than to those of California, although 

 certain recent developments have shown that this rule is not wholly 

 without exceptions. 



