BY R. BROOM. 207 



The premaxillar}^ maxilla, palatine, pterygoid, jugal, and the 

 mandible are all ossified at this stage. The premaxilla is small, 

 -and situated far behind the anterior part of the nasal cartilage. 

 The maxilla is flat, but has two well marked ridges bounding the 

 dental region. The secondary palate is but imperfectly developed. 

 The palatine is large, and forms a good secondary palate. The 

 pterygoid is very small, and, as in Trichosurus, develops in con- 

 nection with the alisphenoid cartilage. 



The malleus, incus, and stapes are shown in fig. 26a( Plate xvi.). 

 The manubrium of the malleus is not fully chondrified. The 

 incus is not unlike that of the higher mammals. The elements 

 are relatively large. 



In Plate xvii., are shown six tj^pical sections through the head 

 of the young Dasyurus. The head was cut into 305 sections, and 

 the number of the section will indicate the plane. 



Section A(fig.47) is the 44th of the series. It passes through 

 the external nasal opening, and shows the condition of the nasal 

 cartilages. The great development of epithelium inside and 

 outside of the mouth, with the fusing of the lips, are well seen. 



Section B(fig.28) is the 75th, and in a plane immediately 

 behind the nasopalatine canal. It shows the nasal septum no 

 longer attached to the alinasal, while the upper part of this 

 latter is passing into the large, lateral orbitosphenoid cartilage. 

 Below the organs of Jacobson lie the paraseptals. The 

 maxillary bone is seen in section with a small secondary palatal 

 plate. Below the tongue is seen the developing mandible, which 

 is ossified considerably in advance of Meckel's cartilage, appear- 

 ing in the 60th section, while the cartilage only appears at the 

 85th. 



Section C(fig.29) is the 122nd, and passes through the middle 

 of the eye. The median cartilage is here broadened out, and 

 fused with the back part of the alinasal. The orbitosphenoid is 

 large, aad appears fused to the median cartilage. The upper two- 

 thirds are well chondrified, but the lower third partly fibrous 

 Portions of the maxilla are seen, and the small jugal is cut across. 

 In the lower jaw Meckel's cartilage is shown, with the mandibular 

 ossification lying on and above it. 



