BY R. BROOM. 573 



differing considerably from the normal mammalian type. In the 

 middle line is a well developed papilla, supported as I have else- 

 where"^ shown by a development of the prenasal cartilage. A 

 section through the middle of the papilla shows on either side a 

 wide Stenson's duct, which at its upper part is roofed over and 

 protected at the sides by the anterior developments of Stenson's 

 and Jacobson's cartilages. Above this is found the cur^-ed 

 cartilage of the nasal floor. 



A short distance behind this plane, in a manner similar to that 

 figured by Herzfeldf in the Lemur, the cartilage of the nasal 

 floor becomes divided into an inner and an outer part, as does also 

 the arched cartilaginous roof of Stenson's duct. The two inner 

 parts unite to form Jacobson's cartilage proper; and the outer to 

 form the hinder part of Stenson's cartilage. This is the condition 

 shown in fig. 1. At the inner side of the upper part of Stenson's 

 duct it is found receiving the duct of Jacobson. 



Almost immediately behind this Stenson's duct is found opening 

 into the nasal cavity (fig. 2). Here Jacobson's duct is small, and 

 lined with squamous epithelium. On this plane there is no 

 ossification in the neighbourhood of the septum, but a very short 

 distance beyond brings us to a plane cutting the anterior part 

 of the prevomer (fig. 3, P.vo.). In a recent paper read before 

 this Societ}"! I called attention to this remarkable bone in 

 discussing the homologies of the palatine process of the pre- 

 maxillary. It is well illustrated in figs. 4 and 5 — the former 

 representing an anterior section; the latter a section near its 

 posterior part. 



On approaching the region of the prevomer, Jacobson's Organ 

 gradually becomes greatly developed, attaining its maximum near 

 the posterior part of the prevomer. \i\ this region the cartilage 

 of Jacobson forms an almost complete tube, only open slightly on 



* Proc. Linn. Soc. N.S.W. 2ncl Ser. Vol. x. pt. 4, 1895. 



t L.c. 

 J Proc. Linn. Soc. N.S.W. 2nd Ser. Vol. x. pt. 3, 1895. 



