TURDUS. . 25 
recognize it with certainty, no birds were obtained. Its note much resembles that of 
Turdus merula. 
No true Blackbird is found in Costa Rica; but in the Andes of South America, and 
in the West-Indian island of Tobago, a second species, Turdus serranus, is commonly 
met with. The close relationship of this species and T. infuscatus to the Old-World 
T. merula is a curious fact of geographical distribution, and probably indicates the 
remains of a much wider dissemination of the ancestral 7. meruda in past times, or that 
a Blackbird inhabiting the high north has been pushed southwards in both America 
and the Old World by advancing cold, and that, in America at least, these birds have 
not followed the returning warmth, but have sought a congenial home in the mountains 
of the south. 
D. SEMIMERULA. 
Major: ptilosis fere unicolor, fusca aut fusco-nigra. Seaxus similes. 
17. Turdus nigrescens. (Tab. IV.) 
Turdus nigrescens, Cab. J. f. Orn. 1860, p. 324°; Lawr. Ann. Lye. N. Y. ix. p. 91°; v. Frantz. 
J. f. Orn. 1869, p. 290°; Salv. P. Z. S. 1870, p. 180°. 
Brunnescenti-nigrescens, alis et cauda nigricantioribus; subtus paulo dilutior; rostro aurantiaco, pedibus 
flavis. Long. tota 10-0, ale 5-5, caude 4:5, rostri a rictu 2-2, tarsi 1-4. (Descr. exempl. ex S. Francisco, 
Costa Rica. Mus. nostr.) 
Juv. subtus gula et pectore cervinis nigro maculatis ; dorsi plumis medialiter cervino notatis. (Descr. ay. juv. 
ex Volcan de Cartago. Mus. nostr.) 
Hab. Costa Rica, Volcan de Cartago (Hoffmann, v. Frantzius, Arcé, J. Cooper), Dota 
Mountains (Carmiol), San Francisco (/ogers) ; Panama, Volcan de Chiriqui (Arcé). 
Turdus nigrescens was first described by Dr. Cabanis from specimens obtained by 
Dr. Hoffmann in the Volcan de Cartago1, and, Dr. v. Frantzius tells us, it is found in 
this volcano at an elevation of from 9000 to 10,000 feet above the sea?. This mountain 
seems to be the head quarters of the species in Costa Rica, as all collectors who have 
worked there have obtained specimens. It is, however, also found in the Dota Moun- 
tains, which lie at no great distance from Cartago. ‘The only other locality in which it 
has been obtained is the volcano of Chiriqui, whence several specimens have been sent 
us by Arcé +. 
This Thrush seems to belong to a South-American section of the genus, found in the 
Andes from Colombia to the neighbourhood of Mendoza, the best-known species of 
which is Turdus gigas. It is, however, a well-marked species, and only remotely allied 
to its next of kin. The sexes present scarcely any difference in plumage. 
BIOL. CENTR.-AMER., Zool., Aves, Vol. 1, Sept. 1879. 4 
