HIEUISDO.— TACHTCINETA. 233 



that it resorts to tlie houses of the city of Mexico for this purpose. In Guatemala 

 we only know it as a migrant, arriving as early as the first days of September and 

 leaving again in April ; but in the former month adult birds are to be seen with 

 young ones in their first plumage. The only record we have of its occurrence in 

 Costa Eica is from its name being included m Mr. Zeledon's list of the birds of that 

 country 22. From the State of Panama, however, we have many skins of both adult 

 and young birds. The latest spring record we have of the appearance of this Swallow 

 in this district is the 7th May, when a bird was seen at sea by Salvin about 100 

 miles from Colon. 



In North America Hirundo erythrogaster is a familiar summer visitant, at which 

 season it spreads over nearly the whole country, including the British Provinces and 

 Alaska, and even straying to Greenland and Bermuda 26. Its habits generally, as 

 well as its mode of nesting, are fully described in works on North-American Orni- 

 thology 4 19. 



TACHYCINETA. 



Tachycineta, CabaniSj Mus. Hein. i. p. 48 (1850) ; Baird^ Rev. Am. B. i. p. 396. 

 Iridoprocne, Cones, B. Col. Vail. i. p. 413. 



This genus was separated by Prof. Cabanis to contain Hirtmdo thalassina and a 

 second but aberrant form, H. hicolor ; this last has since been placed in a distinct 

 subgenus by Dr. Coues, under the name of Iridoprocne ; and with H. bicolor he asso- 

 ciated four other South and Central American species, leaving H. thalassina to stand 

 alone in Tachycineta. The difierence between the last-mentioned species and the rest 

 consists chiefly in its somewhat peculiar plumage, which is soft and like velvet and 

 without metallic gloss. H. hicolor and it allies all have the upper plumage with a 

 rich shining metallic tint. 



From Hirundo Tachycineta differs in the shape of the tail, which is not deeply forked, 

 but only slightly emarginate, the colour, too, of the under surface of all the species 

 is white. 



Like Hirundo, the nostrils open laterally, being overhung by a membrane. 



a. Ptilosis Icevis et velutina, colore metallico absente. (Tachycineta.) 

 1. Tachycineta thalassinus. 



Hirundo thalassina, Sw. Phil. Mag. new ser. i. p. 366 '; Baird, U.S. Bonnd. Surv. ii. Birds, p. 11 '; 



Rev. Am. B. i. p. 399 ' ; Baird, Brew. & Ridgw. N. Am. B. i. p. 347 *. 

 Petrochelidon thalassina, Sol. & Salv. Ibis, 1859, p. 13 %• Scl. P.Z. S. 1864, p. 173 ^ Duges, La 



Nat. i. p. 141 \ 

 Tachydneta thalassina, Sumichrast, Mem. Best. Soc. N. H. i. p. 547'; Coues, B. Col. Vail. i. 



p. 419'. 

 BIOL. CBNTR.-AMBE., Aves, Vol. I., May 1883. 30 



