Anatomy of Notoryctcs typhlops. 79 



In outline the cartilages present in transverse section, that of an 

 ornamental T. This ridge is referred to by Dr. Stirling^, and is 

 well shown in his accompanying figure of the animal. Dorsal to 

 these alinasals lie the forward processes of the nasal bones (n.d.). 

 Further back, the ridge containing the swollen edge of the 

 alinasals, comes to lie more ventralwards, the superior position 

 being taken by another ridge (Fig. 5, s./.r.) with glandular 

 interior, and containing a large duct from the mucous glands 

 posterior to this level. A short distance behind the beginning of 

 the second ridge there arises a process from the arch of the ali- 

 nasal cartilage on each side, connecting each with one of the 

 ventral processes of the nasal septum (n./.r.), so that at this 

 point, and not anterior to it, the nostril is completely enclosed on 

 each side with cartilage. This condition is closely comparable 

 with that in Macro.scelides, as shown in the figures given by 

 Broom'^. Soon there pierces the alinasal cartilages a canal on 

 each side, through which passes one of the naso-lachrymal ducts, 

 which open in front of this, on the ventral surface of the primary 

 lateral ridge into the ventral nasal furrow [v.n./.) on each side. 

 Between the plane of the opening of the naso-lachrymal duct, and 

 that of its passage through the encircling cartilage, I have heen 

 able to trace a splitting off from the ventral surface of the carti- 

 lage of the nasal floor (formed by ventral processes from the carti- 

 laginous septum), of what is at first a thin lamella of cartilage, in 

 three parts. Those on either side lose their connections with the 

 nasal floor except for a while at the extreme outer edge of each, 

 and finally become continuous with the anterior edge of each 

 premaxillary bone. The central portion remains longer in con- 

 nection with the nasal cartilage, so that, in a transverse section 

 taken just at the level of the passage of the naso-lachrymal ducts 

 through the alinasal cartilages, the following relations exist. The 

 nasal septum (Fig. 1, n.s.c.) is very thin and deep, giving off 

 above the two alinasal cartilages {a.c), and ventrally two pro- 

 cesses [n.f.c.) forming the floor of the nasal cavity. Compare 

 in this respect Ornithorhynchus, in which the nasal septum 

 becomes united with these nasal floor cartilajres." This is to be 



1 Stirling: Trans. Roy. Soc. S. Aus., 1891, p. 159, pi. iii. 



2 Proc. Zool. Soc. Lond, 1902, vol. i., pi. x.vi., fig. 1. 



3 Broom: Trans. Roy. Soc. Edin., vol. xxxix., p. 235. 



