1906.] Observations on the Labyrinth of Certain Animals. 293 



The cochlea of the bird consists of a more or less straight tube. It passes 

 a little downwards and then inwards and forwards. There is usually 

 a slight curve on it, with the concavity directed backwards and a little 

 upwards. The main branch of the cochlear nerve runs along the posterior 

 border of the cochlea and sends filaments forwards to the organ of Corti. 

 At the tip of the cochlea, however, the nerve radiates out like a fan into the 

 lagena, and at this spot there is in many birds a saddle-shaped otolith with 

 the concavity directed outwards. 



The ampullae of the semicircular canals of birds differ from those of the 

 mammalia. They are usually set at a more acute angle with the canal 

 as it leaves them. The nerve to the ampulla cuts into it, so to speak, 

 and partially divides the ampulla into two portions, one adjacent to the 

 vestibule and the other adjacent to the canal itself. 



The Labyrinth of the Crested Screamer (Cariama cristata). (Plate 18, fig, 5.) 



The term " crested screamer " is applied to two quite different birds. That 

 from which the labyrinth was taken and prepared by the writer and forms 

 the subject of this description, is closely allied to the cranes and has no 

 relation to Chauna cristata, which is related to the ducks and geese. 

 According to some ornithologists, Cariama cristata is more closely allied 

 to the hawks than to the cranes. The bird lives iu the southern parts 

 of Brazil and Paraguay. It will only fly if hard pressed, the usual method of 

 progress being a stooping run. In some of its habits it is like a bustard, 

 its note is a scream or bark. It lives in the high grass and the habits of 

 the bird are diurnal. 



The labyrinth is rather large for the size of the bird, measuring 15 mm. 

 from the uppermost point on the vertex of the superior canal to the inner- 

 most point at the tip of the cochlea. 



The cochlea is very straight in this bird, the usual curve being almost 

 entirely absent. It measures 6 mm. in length from the front of the round 

 window to the tip of the organ. This is a long cochlea for a bird, that of the 

 ostrich being the only one out of the nine which have been examined that 

 is longer. The diameter of the tube of the cochlea immediately in front of 

 the round window is 2 mm. in length. At the tip of the cochlea the nerve 

 widens out into a spade-shaped structure, and a minute straight otolith is 

 present at this point. 



The vestibule measures 3 mm. in its longest diameter, and there is a very 

 small otolith present in the utricle. The macula negleeta is to be seen close 

 to the opening of the cochlea. 



