440 Supplement to the A. O. U. Check-List. [pus 
July 
The present supplement is made up almost wholly of purely 
nomenclatural changes and represents a considerable portion of 
such cases now pending. The number of additions and changes 
here treated is 32; of ere BE 
{ Wirmer STONE, Chairman 
| H ARRY C. OBERHOLSER, Secretary 
Committee { JonaTHan Dwicur 
ee S. PALMER 
| CHARLES W. RicHmMonp 
ADDITIONS AND CHANGES OF NOMENCLATURE. 
Megalestris Bonaparte becomes Catharacta Briinnich (Ornith. Boreal., 
1764, p. 32), because the latter has for its type, by subsequent desig- 
nation of Reichenbach 1851, Catharacta skua Briimnich, and, further- 
more, is not preoccupied by Catarractes Brisson, a word of different 
classical ending. (Cf. Mathews, Novit. Zool., XVII, No. 3, Dec. 15, 
1910, p. 498; Oberholser, ‘The Auk,’ XXXVI, No. 3, July, 1919, 
p. 418.) The only North American species is 
35. Catharacta skua Briinnich. 
Subgenus Thalasseus Boie becomes Hydroprogne Kaup (Skiz. Entw.- 
Gesch. Nat. Syst. Eur. Thierw., 1829, p. 91; type by subsequent 
designation [Gray, Genera Birds, III, 1846, p. 658], Sterna caspia 
Pallas), because the type of Thalasseus is Sterna sandvicensis Lath- 
am, and Hydroprogne Kaup is the earliest available name for the 
present group. (Cf. Mathews, Novit. Zool., XVII, No. 3, Dec. 15, 
1910, pp. 497-498.) 
Subgenus Actochelidon Kaup becomes Thalasseus Boie, because the 
type of Thalasseus proves to be, by designation of Gray (List Gen. 
Birds, 1840, p. 79) (cf. Stone, Science, N. S., XXVI, No. 666, Oct. 4, 
1907, p. 445; Mathews, Novit. Zool., XVII, No 3, Dee. 15, 1910, 
pp. 497-498), Sterna cantiaca Gmelin (= Sterna sandvicensis Lath- 
am), which designation the previous action of Kaup in proposing 
Actochelidon with the same species as type does not nullify. 
Hydrochelidon Boie becomes Chlidonias Rafinesque (Kentucky Ga- 
zette, 1, No.8, Feb. 21, 1822, p. 3, col.5; type by monotopy, Chlidonias 
melanops Rafinesque (= Sterna surinamensis Gmelin) (cf. Rhoads, 
‘The Auk,’ XXIX, No. 2, April, 1912, pp. 197-198), because the 
latter name has priority. The North American forms of this genus 
are: 
77. Chlidonias nigra surinamensis (Gmelin). 
78. Chlidonias leucoptera leucoptera (Temminck). 
