FOSSIL BIRDS. 457 



Xema sabini (Sabine). Sabine's Gull. 



Larus sabini J. Sabine, Trans. Linn. Soc. Lond., XII, Pt. ii, 1819, 522, 

 (pi. 29). 

 Modern form reported from Pleistocene: Fossil Lake, Oregon. 



Subfamily STERNINAE. Terns. 



Genus CHLIDONIAS Rafinesque. 



Chlidonias Rafinesque, Kentucky Gazette, n. s., I, No. 8, Feb. 21, 1822, 

 3, col. 5. Type, by monotypy, Chlidonias mdaiwps Rafinesque = 

 Sterna surinanicnsis Gmelin. 



Chlidonias nigra (Linnaeus). Black Tern. 



Sterna nigra Linnaeus, Syst. Nat., ed. 10, I, 1758, 137. 

 Modern form reported from Pleistocene: Fossil Lake, Oregon. 



Suborder ALCAE. Auks, Murres, and Puffins. 



Family ALCIDAE. Auks, Murres, and Puffins. 



Subfamily NAUTILORNITHINAE. Nautilornithes. 



Genus NAUTILORNIS Wetmore. 



Naidilornis Wetmore, Ann. Carnegie Mus., XVI, April 10, 1926, 392. 

 Type, by orig. desig., Nautilornis avus Wetmore. 



Nautilornis avus Wetmore. 



Nautilornis avus Wetmore, Ann. Carnegie Mus., XVI, April 10, 1926, 392, 

 pi. 36, figs. 1-8. 



Eocene (bottom of Green River Formation): White River, Utah, 2 miles 

 from Colorado state line. 



Nautilornis proavitus Wetmore. 



Naviihrnis proavitus Wetmore, Ann. Carnegie Mus., XVI, April 10, 1926, 

 394, pi. 36, fig. 9. 



Eocene (bottom of Green River Formation); White River, Utah, 2 miles 

 from Colorado state line. 



