BY R. BROOM. 561 



lateral portions are detached or perforated, as if the whole plate 

 were fundamentally a median structure with lateral expansions. 

 In fig. 6 is represented a transverse vertical section of the snout 

 of the Bandicoot ( Perameles iiasuta) in the plane of the anterior 

 part of Jacobson's Organ. Here there is no distinct ridge in the 

 middle line, and the plate is moderately uniform in thickness. 

 This papillary cartilage has no direct connection with any other 

 cartilage. In fig. 3 is shown a median longitudinal section of the 

 nasal region of a pouch specimen of the common Phalanger 

 (Trichosurus vulpecula, Kerr), illustrating the relations of the 

 small papillary cartilage (?:>.c.). The premaxillary (Pfiix) is seen 

 united with the prevomer which forms its palatine process 

 (p.Pmx): a dotted line indicates the limits of the diff'erent 

 elements as observed in sections slightly out of the mesial plane. 

 The posterior end is found situated near the posterior border of 

 the symphysis of the premaxillary proper, as if it were shut off 

 from its proper relations by the union of the premaxillary with 

 the prevomer. When fig. 6 is compared with fig. 5 representing 

 the condition in the Bat the resemblance between the cartilages 

 of the papillae is most striking; the only important difference is 

 that in the Marsupial the upper portion representing the prenasal 

 proper is lost. While thus we have in the Bat a prenasal carti- 

 lage which gives rise to a support for the papilla, in the Marsupial 

 we have the remains of a similar development, only the papillary 

 portion being left. 



In Klein's'''' paper on the Organ of Jacobson in the Guinea Pig 

 in referring to the relations of Stenson's ducts near their palatal 

 opening he calls attention to "a smaller or larger apparently 

 isolated nodule of cartilage found between the two ducts." This 

 he regards as a detached portion of Stenson's cartilage, but in 

 view of this condition in Marsupials and the Bat I think not im- 

 probable that it may be the rudiment of a prenasal development. 



Fig. 7 represents a section of the • nose of a 6-inch foetal calf. 

 Here the prenasal is well developed and passes between the pre- 

 maxillaries. This condition shows the connection between the 



* Q.J.M.S. Vol. xxi. (ISSl), p. 229. 



