TERTIALS—THICKHEAD 957 
the adults in summer plumage wearing a black cap and having 
the upper parts of the body and wings of a more or less pale 
grey, while they are mostly lighter beneath. They generally breed 
in association, often in the closest proximity—their nests, contain- 
ing three eggs at most, being made on the shingle or among 
herbage. The young are hatched clothed in variegated down, and 
remain in the nest for some time. At this season the parents are 
almost regardless of human presence and expose themselves freely. 
At least half-a-dozen other species have been recorded as occurring 
in British waters, and among them the Caspian Tern, S. caspia, 
which is one of the largest of the genus and of wide distribution, 
though not breeding nearer to the shores of England than on Sylt 
and its neighbouring islands, which still afford lodging for a few 
pairs. Another, the Gull-billed Tern, S. anglica, has also been not 
unfrequently shot in England. All these species are now acknow- 
ledged, though the contrary was once maintained, to be inhabitants 
of North America, and many go much further. 
Mr. Saunders (Cat. B. Br. Mus. xxv. pp. 4-152) recognizes 11 
genera of the subfamily—Hydrochelidon with 4 species ; Phaethusa, 
Gelochelidon, Hydroprocne and Seena with one each—these being 
hitherto most generally placed in Sterna, to which last he allots 33 
species, including among them 3 or 4 that are called in books 
“Sooty Terns,” but by sailors Eac-Brrp (p. 182), or, from their cry, 
WIDE-AWAKES, and seem as much entitled to generic separation as the 
four above named ; Nenia, a very aberrant form, consisting of but 
one species, the Inca Tern, peculiar to the west coast of South 
America ; Procelsterna, Anous and Micranous containing the various 
species of Noppy (p. 643), of which he now admits but 7; and 
(ygis, composed of 2 species of purely white birds, et restricted 
to the southern hemisphere. 
TERTIALS, a name now almost wholly abandoned, but applied 
by older writers to the innermost or proximal cubital REMIGES 
(p. 780), especially when, as in many groups of Birds, they are 
distinctly longer than the more distal or outer. 
TEUCHET and TEWFITT, local names of the LAPWING (p. 504) 
from its cry. 
THICKHEAD, Swainson’s rendering in 1837 (Classif. B. ii. p. 
249) of his own Pachy- 
cephala, a genus named 
by him in 1824 (7rans. 
Linn. Soc. xiv, p. 444, 
note), to which about 
50 species, all charac- PACHYCEPHALA. EoPsALTRIA. 
teristic of and mostly (After Swainson.) 
peculiar to the Australian Region, have been referred, while some 
