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 nasuta) 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 (p.c). The premaxillary (Pmx) is seen 
united with the prevomer which forms its palatine process 
(p. Pmx): a dotted line indicates the limits of the different 
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. (1381), p. 229. 
