HIRUNDO.—TACHYCINETA . 233 
that it resorts to the 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 Rica is from its name being included in Mr. Zeledon’s list of the birds of that 
country **. 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?*. Its habits generally, as 
well as its mode of nesting, are fully described in works on North-American Orni- 
thology 41°. 
TACHYCINETA. 
Tachycineta, Cabanis, Mus. Hein. i. p. 48 (1850) ; Baird, Rev. Am. B. i. p. 296. 
Iridoprocne, Coues, B. Col. Vall. i. p. 412. 
This genus was separated by Prof. Cabanis to contain Hirundo thalassina and a 
second but aberrant form, //. bicolor; this last has since been placed in a distinct 
‘subgenus by Dr. Coues, under the name of Jridoprocne; and with H. bicolor he asso- 
ciated four other South and Central American species, leaving H. thalassina to stand 
alone in Tachycineta. The difference 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. #. bicolor 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 levis et velutina, colore metallico absente. (Tachycineta.) 
1. Tachycineta thalassinus. 
Hirundo thalassina, Sw. Phil. Mag. new ser. i. p. 8661; Baird, U.S. Bound. Surv. ii. Birds, p.11?; 
Rev. Am. B. i. p. 299°; Baird, Brew. & Ridgw. N. Am. B. i. p. 347 *. 
Petrochelidon thalassina, Scl. & Salv. Ibis, 1859, p. 13°; Scl. P.Z. S. 1864, p. 173°; Dugés, La 
Nat. i. p. 141”. 
Tachycineta thalassina, Sumichrast, Mem. Bost. Soc. N. H.1. p. 547 *; Coues, B. Col. Vall. i. 
p- 419°. 
BIOL. CENTR.-AMER., Aves, Vol. L., May 1883. 30 
