BY R BROOM. 
483 
advocated by Wilson.* In his paper published by this Society 
he gives a very accurate and minute description of the bone and 
its relations, and gives reasons for considering the bone to be a 
true vomerine element and no part of the premaxillary. His 
main arguments maybe briefly summarised as follows : — (1) That 
as the posterior part of the palatine plate of the dumbbell bone 
rests on the "cartilage of the nasal floor " it is on a higher plane 
than the maxillary palate ; (2) that the vertical part is prolonged 
backwards for a considerable distance dorsad of the maxillary 
plane, and " that a bone which is so prolonged backwards on a 
higher plane than the maxillary palate cannot be regarded as 
developed in the same morphological plane with it"; and (3) that 
the posterior spur is separated from the maxillary palate by 
a peculiar hiatus. These arguments afford practically con- 
clusive proof that the dumbbell-shaped bone belongs to the 
vomerine category and is no part of the premaxillary; and to 
Wilson thus belongs the credit of having first clearly recognised 
the vomerine nature of the bone. But on the other hand, while 
the above arguments show that the bone is not part of the pre- 
m axillary, the}^ rather support than disprove its homology with 
the element usually called "palatine process of the premaxillary," 
and Wilson himself recognises the weight of evidence in favour 
of this homology; and when once it becomes recognised that the 
palatine process of the premaxillary is itself a distinct vomerine 
element anchylosed or formed in connection with the premaxillary 
the difficulty of reconciling the two views at once disappears. 
W. 1ST. Parker,f in his recent paper on Echidna, gives a section 
of a young Ornithorhynchus skull which shows the dumbbell- 
shaped bone developing as bony splints to ' the cartilages of 
Jacobson in exactly the same manner as Kitchen Parker has 
* J. T. Wilson, " Observations upon the Anatomy and Relations of the 
dumbbell-shaped bone in Ornithorhynchus, with a new theory of its 
homology, &c." Proc. Linn. Soc. N.S.W. 1804. 
t W. N. Parker, "On some points in the Structure of the Young of 
Echidna aculeata." Proc. Zool. Soc. 1894. 
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