The Chondrocranium of aii Embryo Pig. 205 



lateralis anterior. This process divides the fenestra narina into 

 two parts, a larger anterior (destined for the external narial aperture 

 of the adult) and a smaller posterior, through which the ductus 

 naso-lacrymalis passes to open into the nasal chamber. The former 

 opening is produced backwards by a slender notch in the side of 

 the nasal capsule just in front of the origin of the cartilage lateralis. 



The fenestrce crihrosoe are, as yet, simple triangular openings, 

 one on each side of the posterior half of the nasal septum, which, 

 dividing them, forms the crista galli. There is no indication of 

 the cartilaginous bars which later divide the fenestrse and form the 

 cribriform plate (lamina cribrosa). Each fenestra is in the form 

 of an isosceles triangle, of which one side is only about half as long 

 as the other two. The sharp corner is directed posteriorly, while 

 the short side, which is bowed outward, is anterior and lateral. Each 

 fenestra is nearly horizontal; the lateral angle is raised slightly 

 above the level of the other two. Attached at this angle is the com- 

 missura spheno-ethmoidalis, which connects the capsule with the ala 

 orbitalis. 



The nasal cavity can be divided conveniently into a pars 'posterior 

 or, subcerebralis, lying ventrally to the fenestrse cribrosae and a 

 pars anterior. The maxilloturbinal, the homolog of the reptilian 

 concha, is formed by the inrolled lower margin of the paries nasi. 

 It lies in the floor of the recessus or pars anterior, and extends from 

 the lamina transversalis anterior to the ductus nasopalatinus. 

 Medianly it presents a flat surface, but as yet there is no splitting 

 to form the double-rolled turbinal of the adult. The nasoturbinal 

 is located internal to the pit mentioned above, (p. 202) which lies 

 in front of the bulging recessus lateralis. Internally it presents a 

 low vertical lamella and a forwardly projecting ridge, which together 

 form a — ( shaped turbinal. This seems to be the typical mamma- 

 lian shape. 



The pars posterior lies almost entirely ventral to the anterior 

 part of the cerebrum and beneath the large fenestra cribrosa. Voit, 

 in a forthcoming work on Lepus, divides its cavity into a recessus 

 lateralis and a recessus posterior or ethmoturhinalis, the two being 

 separated by a vertical plate (PL I, ethmoturh.) This is the first 



