PRIMORDIAL CRANIUM OF THE CAT 393 



all. Peter ('06) seems to regard the mammalian gland as a 

 new acquisition. It will be remembered, however, that the lat- 

 eral nasal gland in the cat embryo of 23.1 mm. is located just in 

 front of the base of the crista semicircularis. 



Next, we may attempt to compare that part of the nasal wall 

 (paranasal cartilage), which stands just behind the fissure in 

 the cat, and the aditus conchae in Uzard. We have seen that 

 the commissura spheno-ethmoidahs unites, in cat embryos of 

 17 mm., with the dorsal margin of the paranasal cartilage, 

 where the latter bounds the olfactory fenestra, thus presenting 

 relations which recall those between the posterior half of the 

 .side wall of the nasal capsule and the cartilago spheno-eth- 

 moidalis of Lacerta. For, at the junction of these parts, in the 

 cranium of the lizard, the lateral wall hmits by its upper margin 

 the olfactory fenestra while, medially, it passes into the posterior 

 wall, the planum antorbitale, as is also true for the cat. It 

 has been noticed that the ventral and anterior margins of the 

 paranasal, are continuous inrolled edges, which form the car- 

 tilaginous maxillo-turbinal and, with the free posterior margin 

 of the parieto-tectal cartilage, form the beginning of the crista 

 semicircularis. In Lacerta, the part of the side wall in question 

 goes over anteriorly into the lateral overhanging plate of the 

 bilaminar concha, the medial plate of which is the direct continua- 

 tion of the side wall of the anterior half of the nasal capsule. 

 Furthermore, the lateral plate passes ventrally into the floor of 

 the recessus extraconchalis. Of great interest is the resemblance 

 between the concha and floor of the recessus extraconchalis of 

 Lacerta on the one hand and the crista semicircularis and maxillo- 

 turbinal of the cat on the other. 



This comparison brings out a certain degree of similarity of 

 form and relation between the skeletal parts of the region of the 

 recessus extraconchalis of Lacerta (embryo of 31 mm. total 

 length) and of the recessus lateralis of the cat (embryos of 17- 

 20 mm.). An opinion as to a possible homology between these 

 parts should not be ventured on a comparison limited to the 

 data here presented. Greater knowledge of the development of 

 the ethmoidal skeleton in the hzard is required, and additional 



JOURNAL OF MORPHOLOGY, VOL. 29, NO. 2 



