BY R. BROOM. 593 



Phascologale peniciUata, Shaw, (mammary foetus, head length 

 9 mm.). The nasal-floor cartilage in front of the naso-palatine 

 canal is present as a well developed, slightly curved plate of 

 cartilage passing outwards from the base of the septum and 

 forming a complete floor to the nasal cavity, uniting laterally 

 with the alinasal. On nearing the naso-palatine canal, its inner 

 end becomes detached from the septum and curves upwards and 

 slightly outwards (PL XLi. fig. 10). The naso-palatine canal passes 

 somewhat obliquely backwards, as well as upwards, so that in 

 vertical section it is seen connecting the nasal cavity with the 

 mouth. On its passing upwards the premaxillary is seen to 

 separate from its palatine process as if to make a passage (fig. 10), 

 and a little behind this the nasal-floor cartilage divides into its 

 inner and outer parts. The outer part, which is small, disappears 

 almost immediately behind tliis plane; but the inner part, or 

 Jacobson's cartilage, is well developed and appears as an upx'ight 

 plate with a large process passing outwards from its upper end 

 and forming a support to the inferior septal ridge."^ The lower 

 part is sujiported on its lower and inner side by the developing 

 palatine process of the premaxillary. 



In fig. 1 1 the naso-palatine canal has lost its connection with 

 the mouth, and above is seen to receive the opening of Jacobson's 

 duct on the inner side, and on its outer side to be connected with 

 the nasal cavity. Jacobson's cartilage is here well developed, 

 receiving Jacobson's duct or organ in its concave outer side. If 

 this section be compared with the similar section in the young 



* This ritlgp, which extends along on each side of the base of tlie septum, 

 has been generally referred to as the " glandular ridge." The term, how- 

 ever, is inappropriate, as the ridge is often quite devoid of glandular tissue, 

 and I have therefore proposed the above term instead and in contradistinc- 

 tion to a much more typically glandular ridge frequently present in the 

 upper and middle septal region, which may be called the " superior septal 

 ridge." In the present papci-, as only the lower septal region is under 

 consideration, wheu the term "septal ridge" occurs, the inferior septal 

 ridtje will be understood. 



