Barrows.] 154 [April 4, 



Coll. La Fresnaye, No. 8132, Society's Coll., No. 9206; N. Europe; 

 mounted. 



Coll. La Fresnaye, No. 8133, Society's Coll., No. 9207; N. Atlan- 

 tic; mounted. 



Coll. La Fresnaye, No. 8134, Society's Coll., No. 9208; N. Amer- 

 ica; young; mounted. 



Duplicate, no number; Dr. Shattuck. 



4. Fratercula monocerata. 



Alca monocerata Pall., 1811. Cerorliina monocerata Cassin. Cera- 

 torliina (Uria) occidentalis Aud. 



Bill strongly compressed ; lower mandible entirely smooth on its 

 sides; upper one smooth as far back as anterior point of nostrils, 

 where begins the root of a " horn," which seems to be saddled on the 

 base of the upper mandible, and rises about one-third of an inch 

 above the culmen. The part of the horn which extends down on the 

 side of the bill is a little above the level of the remainder of the lat- 

 eral surface of the bill, and thus a slight furrow is produced, which 

 is curved, and has its concave side toward the point of the bill; just 

 in front of this furrow, the surface is slightly wrinkled. The base of 

 the horn is a little wider than the nostril which opens beneath it, but 

 it narrows toward the apex, which is rounded. The size and extent 

 of the horn, in the direction of the length of the bill, varies very 

 much in different individuals, but it is always strongly compressed. 

 Between the posterior margin of the horn and the line of feathers, 

 there is a narrow band of, unfeathered, horny membrane, which evi- 

 dently replaces the punctate ridge found in the three preceding 

 species. The culmen is decidedly convex ; the gonys slightly con- 

 cave; just at its angle, which is well marked, and partially separating 

 the rami, which are evident, is a supernumerary corneous piece from 

 one-fourth to one-half an inch in length, and about one-sixteenth of 

 an inch in depth, which looks as though moulded on after the full 

 development of the rest of the bill. 



The general color above is black, most glossy on the back and 

 wings, rather duller on the head, and changing gradually to dark 

 ash on the sides of the head and neck and on the throat; the color 

 becomes lighter on the breast, and so extends along the sides to the 

 flanks. The belly and under tail coverts are nearly pure white. 

 There are two sets of stiff, lanceolate, white feathers on the sides of 

 the head; one originating just over the eye and running straight 

 backward; the other beginning near the angle of the mouth and 



