BY R. BROOM. GOl 



process, and ultimately all that is left of it is a small plate lying 

 over the upper and inner side of the reduced posterior end of the 

 organ. 



Peraiueles nasuta, E. Geoff., (half grown and adult). Between 

 the adult and half grown condition the chief differences are due 

 to the fact that in the adult the bony development is greater and 

 the cartilaginous elements more degenerate. In the following 

 account it is the half grown specimen that is being described 

 unless otherwise stated. 



In the region immediately in front of the incisor teeth, the 

 nasal septum is rather broad and at its base has on each side a 

 well developed inferior septal ridge. The nasal-floor cartilage is 

 relatively feeble on the whole, but its inner part is better 

 developed and turns up close against the septum, then curves 

 outwards to form the support of the septal ridge. On reaching 

 the plane of the first pair of incisors, the only difference worth 

 noting is that the septum has retreated somewhat, and only the 

 inner part of the nasal-floor cartilage remains. 



In the adult, even in the region of the predental portion of 

 the premaxillary, the nasal-floor cartilage is represented by little 

 more than the inner part. 



In the plane of 2nd incisor in the half grown specimen the 

 nasal-floor cartilage is represented only by the skeleton of the 

 ridge, while on the same plane the premaxilla is seen sending up 

 a process towards the base of the septum. In the anterior 

 papillary region, as seen in fig. 5, the cartilage is found present 

 as an inner plate and an outer bar. Though this is in front of 

 the naso-palatine canal, as there is no outer part of the nasal-floor 

 cartilage, it will be better to call it Jacobson's cartilage, for 

 though there is no organ at this point, from the condition of the 

 cartilages and other structures it is highly probable that the 

 organ once extended forwards considerably in advance of its 

 opening into the naso-palatine canal, as is the case in Ornitho- 

 rhynchus. As it is, the organ still e.xtends some little way in front 

 of its opening into the naso-palatine canal, and on one side of 

 fiu. 6 the anterior extension is seen cut across. 



