ON THE HOMOLOGY OF THE PALATINE PROCESS 
OF THE MAMMALIAN PR EM AXILLARY. 
By R. Broom, M.B., CM., B.Sc. 
In typical mammals the premaxillary bone may be divided into 
two more or less well marked parts. There is the anterior and 
outer part bearing the incisor teeth and forming the outer wall 
and floor of the nasal cavity at its anterior part, and there is 
generally an elongated delicate process of bone passing backwards 
into the palatine region — the palatine process of the premaxillary. 
Throughout the Mammalia the tooth-bearing part of the pre- 
maxillary varies comparatively little; but in the palatine process 
even in closely allied forms we have the most striking variations. 
Among Marsupials, for example, in the genus Trlchosuras the 
palatine process is exceedingly long, while in the closely allied 
Phascolarctus it is only slightly developed. 
Opinion seems to be considerably divided as to whether the 
premaxillary is a single structure, or whether it is in reality 
composed of two distinct elements. Albrecht,* Suttonf, and 
Parker | have shown that the palatine process may be distinct in 
origin from the body of the premaxillary through becoming early 
united with it, and Howes§ states as the result of a special 
* P. Albrecht, " Sur la Fente maxillaire doable sousmuqueuse et les 4 os 
intermaxillaires de 1' Ornithorhynque adulte normale." (Bruxelles, 1883). 
P. Albrecht, " Die morphol. Bsdeutung der seitlichen Kieferspalte, &c." 
Zool. Anzeiger, 1879. 
t i. B. button, " Observations on the Parasphenoid, the Vomer and the 
Palato-pterygoid Arcade." Proc. Zool. Sue. 1884, p. 566 
X W. K. Parker. " On the Structure and Development of the Skull in 
the Mammalia," Pt. ii Edentata ; Pt. iii. Insectivora. Phil. Trans. Koy. 
Soc. Lond. 1885. 
§ G. B. Howes, " On the Probable Existence of a Jacobson's Organ among 
the Crocodilia, &c." Proc. Zool. Soc. 1891. 
