5/6 DR. J. SYMINGTON ON THB [NoV. 17, 



to one of my Australian pupils, Mr. C. Hardcastle, not only for 

 procuring rae the specimen, but also for the trouble he took to have 

 it carefully hardened. 



In consequence of the elongated form of the face, the position of 

 the nostrils towards the anterior end of the beak, and the prolongation 

 of the hard palate backwards nearly as far as the glenoid cavity, the 

 nasal cavities are of considerable length. In my specimen, which 

 measured 37 cm. from the tip of the bill to the posterior extremity 

 of the tail, the nasal cavities were 6 cm. in length. Males are con- 

 siderably larger than females, and Mr. Oldfield Thomas (7) found 

 the basal length of the skull of an adult male, measured from the 

 basion to the anterior end of the premaxillary bones, to be 10'8 cm. 

 The nasal cavities are not, of course, equal to the basal length of 

 the skull, but in this male they would be quite 8 cm. ; while the 

 nasal cavities are very long their transverse and vertical diameters 

 are very slight, so as to make their naked-eye examination somewhat 

 difficult. The anterior parts of the nasal cavities are flattened, like 

 the bill, from above downwards, and here the transverse diameter 

 is about 4*5 mm. and the vertical extent scarcely 2 mm. Farther 

 back, under the cranial cavity, and especially in the region of the 

 turbinated processes, the nasal cavities are much deeper, measuring 

 I'rom the roof to the floor 5 mm., while their transverse diameter is 

 almost obliterated by the projection of the turbinals from the outer 

 wall. 



Vertical transverse sections of the nasal cavities immediately 

 behind the nostrils show a subdivision of each cavity into 3 com- 

 partments — superior, middle, and inferior (see Plate XLIII. fig. 1). 

 The two septa between these compartments are formed by the lining 

 membrane of the nose, which is here composed of dense connective 

 tissue, the matrix of which is only slightly fibrillated, and of stratified 

 squamous epithelium. The septa are not supported by any skeletal 

 framework, but contain a few small glands the ducts of which open 

 into the middle compartment. Serial sections show that the septa 

 commence anteriorly as horizontal ridges projecting from the sides 

 of the partition between the two nostrils and unite with the outer 

 walls of the nasal cavities just behind the two nostrils. In my 

 sections the middle compartment is always larger than the others, 

 but this diff'erence becomes more obvious as one passes backwards, 

 the superior and inferior compartments gradually becoming smaller 

 and ultimately end blindly, while the middle one becomes continuous 

 with the main cavity of the nose. The two caecal pouches extend 

 backwards to a little beyond the anterior end of Jacobson's organ 

 and nearly as far as the naso-palatine foramen. Their length is 

 about 3 mm., and the upper is a trifle longer than the lower. 



J. F. Meckel is the only author who, so far as I have been able 

 to ascertain, makes any reference to this peculiar arrangement. In 

 plate vii. fig. 8 of his classical work on the Ornithorhynchus (1), he 

 gives a view of the anterior part of the right nasal cavity with its 

 three divisions. He exposed them by cutting through the outer 

 wall of the nose and turning its roof over to the left side. Meckel 



