460 7. IRIS—IVORY-BILL 
body, but generally now restricted to the organs of the DIGESTIVE 
SYSTEM. 
IRIS (plural Irides), the coloured ring surrounding the pupil of 
the EYE. 
IRRISOR, the generic name, since adopted as English, pro- 
posed by Lesson in 1831 (Zraité @ Orn. p. 239) for an African bird, 
the Upupa erythrorhynchus of Latham, which had hitherto been so 
variously assigned that its affinities were uncertain, and so they 
remained until Dr. Murie (Jhis, 1873, pp. 181-211, pls. v.-vii.) 
proved that the surmise of its original describer and of Strickland 
(Ann. Nat. Hist. xu. pp. 238-243) in referring it to the Upupide 
(Hoopor) was not far wrong, though, along with Rhinopomastus an 
allied genus named by Andrew Smith and established by Jardine 
in 1828 (Zool. Journ. iv. p. 2, pl. 1.), it might be justifiably placed in 
a separate Family. No fewer than 10 species of Jrrisor, one of 
which has been further generically distinguished as Scoptelus, have 
been described, and 3 of Rhinopomastus; but perhaps there are 
not really so many. All are African, recognizable by their more 
or less curved bill, glossy purple or steel-blue plumage, with a white 
patch on the wing, and white on at least the outer feathers of the 
tail, which is commonly elongated. They are wholly arboreal in 
their habits, thereby differing from the Upudidx, and unceasingly 
seek their food in the insects that frequent the bark of trees. The 
commonest species of the Cape Colony, J. erythrorhynchus has, ac- 
cording to Mr. Layard (B. S. Africa, p. 73), a harsh cry, and is 
ealled by the Dutch Kackela, meaning “chatterer.” Another, £. 
cyanomelas, also occurs in South Africa. 
ISCHIUM, or Os ischii, the posterior and ventral, or middle 
bone of the three that form each half of the PELVIS, and meet at 
the acetabulum or cup which receives the head of the FEMUR. 
IVORY-BILL, an abbreviation of Ivory-billed WoopPEcKER, 
so called from the colour of its beak, Picus or Campephilus prin- 
cipalis, the largest 
species of the 
Family inhabiting 
the United States 
of America, and 
except its more 
southern relative P. or C. imperialis the largest of the Picidz. 
Though said to have been met with in Maryland, North Carolina 
seems to be the northern limit of its ordinary range in the east, and 
CAMPEPHILUS PRINCIPALIS. (After Swainson.) 
' In this case the name of the Family should be Family Rhinopomastide 
from the oldest genus in it, not Jrrisoride as often given. 
