90 CLA IVS— CL OA CA 



Dromaius, 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 Phasianidse. 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 faeces, 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 " urodseum " is small, and receives 

 in its dorso-lateral walls the ureters and the genital ducts, which are 

 protected by papillse. 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 miiscle, lodges 

 the copulatory organ, and on its dorsal wall leads through a wide 

 opening into the hirsa Fahricn. 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 "coprodaeum," is situated above the 

 urodgeum, is mostly an oval dilatation of the rectum, and is of 

 considerable size in those birds whose faeces are very fluid, as 

 Accipitres, Herodii, and Steganopodes. In Casuarius and Rhea 

 it passes gradually into the rectum above, but in many Carinat?e, 

 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 rcndus, 

 1856, xliii. p. 412) as a new species under the name of Morula dadyloptera. 



