Anatomy of Acanthidositta chloris. 613 



diagrammatic characters. As to Acanthidositta, he remarks 

 that it agrees, in the structure of the syrinx, in every essential 

 respect with Xenieus. 



The Intestinal Convolutions and Gizzard. 



The intestinal convolutions, unravelled on Dr. Chalmers 

 Mitchell's system, are of the type which he has shown to 

 be characteristic of the Passerines. 



The gizzard when opened displayed certain characters in 

 the lining membrane worthy of record. 



The cardiac extremity, as far as the level of the cardiac 

 and pyloric apertures, was lined with a simple mucous mem- 

 brane ; all the remaining cavity below these apertures was 

 thrown into longitudinal folds, transversely striated and of 

 a chitinous texture. 



Osteology. 



The skeleton of Acanthidositta presents many striking 

 points of resemblance with the Synallaxine skeleton, upon 

 which we shall enlarge presently. 



The Skull (PI. XIII. figs. 1-5). — One of the most striking 

 superficial characters of the skull of Acanthidositta is the 

 marked depression and great width of the cranium. The 

 interorbital region of the frontals is much constricted. 

 There is a well-marked cerebellar prominence, but the supra- 

 foraminal and lambdoidal ridges are ill-defined. The lateral 

 occipital wings are but feebly developed, forming but a low 

 ridge caudad of the tympanic membrane. 



The basitemporal plate is inflated so as to form a pair of 

 tumid swellings separated by a median groove. By the 

 fusion of its free edge with the ossified connective tissue 

 forming the anterior wall of the recessus tympanicus anterior, 

 the Eustachian grooves have been converted into closed 

 channels. The parasphenoidal rostrum is long and slender, 

 and passes abruptly forwards from the cranium. 



The tympanic cavity is moderately large, shallow, oval in 

 outline, and looks downwards, outwards, and forwards. The 

 mesial border of its slightly raised rim extends inwards as far 

 as the level of a line running parallel with the long axis of 



