go CLA WS—CLOACA 
Dromeus, and Apteryx. Probably many more birds will be found 
in which such fingernails have remained dormant as latent germs 
and have individually been revived; but the taxonomic value of 
these ancestral vestigial structures is nil. 
Spurs are claws and nails in a different sense. They are 
generally conical, consisting of a horny sheath which surrounds a 
bony core produced by the supporting bone. Hereto belong those 
on the metatarsus of many Phasianide. Similar structures occur 
on the bones of the wrist and hand, namely a long and sharp 
spur with strong bony core on the radial side of the first and 
one on the second metacarpal bone in Chauna derbiana; on the 
first metacarpal in Parra and in Hydrophasianus ; and on the radial 
carpal bone in Plectropterus. The large exostoses of the size of a 
walnut on the wrist of the male Pezophaps were probably likewise 
covered with a thickened horny layer, and were, like all these 
structures, used as weapons. Young spurs can be easily grafted on 
various parts of other animals. 
CLOACA, the dilated terminal portion of the alimentary canal, 
which opens through the vent, and besides the feces, discharges 
the urine and the genital products. The whole cloaca of most birds 
is divided by transverse folds into a vestibulum, a urino-genital 
or middle, and a rectal or innermost chamber. 
The urino-genital chamber or “ urodeeum” is small, and receives 
in its dorso-lateral walls the ureters and the genital ducts, which are 
protected by papillz. Above their orifices is a circular fold, most 
prominent on the ventral side; below them, towards the vent, is 
another well-marked circular fold, which, towards the ventral 
aspect, passes into the coating of the copulatory organ, when 
such is present. The space between this fold and the outer 
anal opening, which is closed by a strong sphincter muscle, lodges 
the copulatory organ, and on its dorsal wall leads through a wide 
opening into the bursa Fabricii. This organ is peculiar to birds, is 
most developed in the young of both sexes, and often becomes 
more or less obliterated in the adult; its function is still unknown ; 
it certainly is not a lymphatic gland, and the occurrence of sperma 
in it is accidental. 
The innermost chamber, or “ coprodzeum,” is situated above the 
urodzeum, is mostly an oval dilatation of the rectum, and is of 
considerable size in those birds whose feces are very fluid, as 
Accipitres, Herodii, and Steganopodes. In Casuarius and Rhea 
it passes gradually into the rectum above, but in many Carinatee, 
as well as in Struthio, the upper end is marked by a strong circular 
fold, and the inner surface of the walls is smooth and different from 
one of the Blackbird, from Syria, was described by Bonaparte (Comptes rendus, 
1856, xliii. p. 412) as a new species under the name of Merula dactyloptera. 
