Bawd£n, Nose and Jacobson's Organ. 129 



nose, etc. The olfactory cavity is first enclosed with a 

 cartilaginous or bony investment in Elasmobranchii. Poly- 

 pterus, the most highly developed of the fishes, has a com- 

 plicated system of folds around a spindle. These compartments 

 increase the surface of the cavity, a nerve passing to each fold. 

 In Dipnoi and Perennibranchiata there is an external perfor- 

 ated cartilaginous capsule. In Amphibia true turbinals first ap- 

 pear, processes of the cranial skeleton which serve to increase 

 the epithelium exposure. These spaces and cavities attain to 

 considerable development in Anura. 



Born has very fully dealt with the bony environment as 

 found in adult Anura, taking Rana esculenta as an example. 

 In Crocodilia and onwards, the olfactory organ is situated farther 

 backwards, the posterior part lying immediately below the brain. 

 In birds we have one true turbinal and two pseudo-turbinals, 

 while in mammals the surface is increased by three methods ; 

 the formation of the hard and soft palate, the development of 

 the turbinal bones, and the formation of the accessory cavities 

 of the nose. 



The type chosen in the present studies for delineating the 

 nasal cartilaginous investment in Amphibia is a specimen of 

 Urodela, Amblystoma pnnclatam taken at about the time of the 

 metamorphosis. The description of the type before us is based 

 on a close comparison of the specimen under investigation with 

 the description of the investment of an adult Axolotl, and Am- 

 blystoma opacum which is a North American species developed 

 from an Axolotl form. This description is found in "The 

 Morphology of the Skull," by W. K. Parker, (No. 20.) 



The broad flat inter-nasal tract of cartilage in Figs. 1-1 5, 

 Plate V, occupies only about one-third of the longitudinal axis 

 of the skull, while its breadth is approximately the width of the 

 head. It has a concave margin behind, in which is lodged the 

 fore part of the brain. The anterior margin is also concave 

 where the two trabecular cornua separate. The olfactory crura 

 pierce the shelving front wall of the cranium (in the internasal 

 plate) just on the inner surface. The cartilaginous processes of 

 the nasal plate nearly meet externally and in one case actually 



