TABLE OF CONTEXTS. XT 



Page. 



Key to the Species of Thalasseus 467 



2. Thalasseus maximus (Boddaert) 467 



3. Thalasseus elegans (Gambel) 472 



4. Thalasseus eurygnathus (Saunders) 474 



5. Thalasseus sandvicensis acuflavidus (Cabot) 476 



Genus 3. Gelochelidon Brehm 478 



6. Gelochelidon nilotica (Gmelin) 479 



Genus 4. Sterna Linn?eu3 485 



Key to the Species of Sterna 486 



7. Sterna trudeaui Audubon 488 



8. Sterna forsteri Xuttall 490 



9. Sterna hirundo Linnaeus 493 



10. Sterna paradisaea Briinnich 499 



11. Sterna dougalli Montagu 505 



12. Sterna aleutica Baird 510 



13. Sterna ansetheta recognita Mathews 512 



14. Sterna angetheta nelsoni Ridgway ; 514 



15. Sterna fuscata fuscata Linmieus 514 



16. Sterna fuscata crissalis La\rrence 519 



Genus 5. Sternula Boie 520 



Key to the American Species and Subspecies of Sternula 520 



17. Sternula antillarum antillarum (Lesson) 521 



18. Sternula antillarum browni (Mearns) 525 



Genus 6. Hydrochelidon Boie 526 



Key to the Species and Subspecies of Hydrochelidon 527 



19. Hydrochelidon leucopareia (Temminck'^ 528 



20. Hydrochelidon nigra surinamensis (Gmelin^ 532 



21. Hydrochelidon leucoptera (Temmiuck) 536 



Genus 7. Phsetusa Wagler 540 



22. Phsetusa chloripoda (Vieillot) 541 



Genus 8. Anous Stephens. 544 



Key to the American Subspecies of Anous stolidus 545 



23. Anous stolidus stolidus (Linnaeus) 546 



24. Anous stolidus ridgwaj-i Anthony 550 



25. Anous stolidus galapagensis (Sharped 551 



Genus 9. Megalopterus Boie 552 



Key to the Species and Subspecies of Megalopterus 553 



26. Megalopterus minutus atlanticus Mathews 554 



27. Megalopterus minutus diamesus (Heller and Snodgrass) 556 



Genus 10. Gygis Wagler •. 557 



Key to the Species of Gygis 558 



28. Gygis alba Candida (Gmelin) 559 



Family Larid.e. The Gclls 561 



Key to the Genera of Laridse 562 



Genus 1. Rissa Stephens 564 



Key to the Species and Subspecies of Rissa 565 



1. Rissa tridactyla tridactyla (Linnaeus') 565 



2. Rissa tridactyla pollicaris Stejneger 571 



3. Rissa brevirostris (Bruch) 573 



Genus 2. Pagophila Kaup 575 



4. Pagophila alba (Gunnerus) 576 



Genus 3. Larus Linneeus 5S0 



