Three eggs, two from Anderson River and one from Great Slave Lake, range from 1.53 to 1.60 inches in length, and from 1.20 to 1.22 in breadth, their average measurements being 1.56 by 1.21. They have a ground-color of a rich reddish-cream, very generally covered with blotches and finer markings of reddish-brown, deepening in places almost into blackness, and varying greatly in the depth of its shading, with a few lines of black. In one the red-brown is largely replaced by very fine markings of a yellowish sepia-brown, so generally diffused as to conceal the ground and give to it the appearance of a light buff. Mr. Ridgway, after a careful analysis of the varying markings and sizes of twenty-one eggs, has kindly given the following:— “Extremes of twenty-one eggs (mainly from Forts Yukon, Anderson, Resolution, and MacKenzie rivers): largest (10,687, Yukon, June), 1.75 × 1.28; smallest (8,808, Anderson River, June), 1.55 × 1.20. The ground-color varies from creamy-white to deep purplish-rufous, there being one egg (4,090, Great Slave Lake, June 6, 1860) entirely and uniformly of the latter color; the lightest egg (normally marked, 2,663, Saskatchewan) is creamy-white, thickly sprinkled with dilute and deep shades of sepia-brown, thickly on large end, and sparsely, as well as more finely, on the smaller end. The markings vary in color from dilute indian-red to blackish-chestnut. “_H. richardsoni_ is larger than _columbarius_, and probably has a larger egg. There are no eggs such as Richardson describes in the series of _columbarius_ in the Smithsonian Collection.” The var. _richardsoni_ was recognized by Richardson as distinct from the more common _columbarius_; and a single specimen, killed at Carlton House, and submitted to Swainson, was pronounced by him, beyond doubt, identical with the common Merlin of Europe. Other specimens have since been procured, and are now in the Smithsonian Collection. They are recognized by Mr. Ridgway as identical with Richardson’s bird, but quite distinct from the _Æsalon_ of authors. He has named the species in honor of its first discoverer. Of its history and habits little is known. A single pair were seen by Richardson in the neighborhood of Carlton House, in May, 1827, and the female was shot. In the oviduct there were several full-sized white eggs, clouded at one end with a few bronze-colored spots. Another specimen, probably also a female, was shot at the Sault St. Marie, between Lakes Huron and Superior, but this was not preserved.