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﻿ and the bears. Neither of these quadrupeds has the gradation of color, nor the standing or crouching habit. They are both nocturnal, and therefore do not need either gradation or crouching for concealment.

It is plain, then, that while nature undeniably completes the concealment of animals by pitching their whole color-gradation in a key to match their environment, the real magic lies in the gradation itself from darkest above to lightest below, wherever this gradation is found. This is why it is so hard to see the Partridge in the tree, the Sandpiper on the mud, or the tiger crouching in the jungle.

DESCRIPTIONS OF A NEW HORNED LARK AND A NEW SONG SPARROW, WITH REMARKS ON SENNET'S NIGHTHAWK

The birds upon which this paper is based were collected by Mr. W. H. Hoyt and myself in Towner and Rolette Counties, North Dakota, during the spring and summer of 1895. Both counties belong to the prairie region, are practically treeless, cul- tivated only partially, and dotted with lakes and sloughs of vary- ing extent. The Turtle Mountains, part of which lie in the northern part of Rolette County, and through which passes the Manitoba boundary, are utterly different in character. They con- sist of hills rising a few hundred feet above the rolling prairie, contain numberless small lakes and ponds, and are covered with a dense growth of deciduous trees. My thanks are due to Mr. Hoyt for the use of his series of skins of the races described, and to Dr. Allen and Mr. Chapman of the American Museum of Natural History, and to Mr. Ridgway of the Smithsonian Institution, for the privilege of comparing my birds with the collections of the respective museums.