196 EDWARD L. RICE 
cartilage stage of Vipera Peyer (’12) describes the floor as con- 
sisting of practically nothing beyond an isolated shell for the 
support of Jacobson’s organ, although he recognizes procartilage 
connections with the septum and the lateral wall; Born (’83) 
has recorded a somewhat less rudimentary condition in Tropi- 
donotus and Pelias. The paraseptal cartilages are generally 
present throughout the group, but lacking in snakes (Peyer, 712). 
They are interpreted by Gaupp (’06), following Seydel (96), 
as mere detached portions of the floor; before chondrification 
Gaupp (05 b) reports them continuous with the septum in the 
lizards. Their separation from the septum is simply one item 
in the general process, already discussed in connection with the 
planum antorbitale, through which the posterior end of the nasal 
capsule becomes free for its change of position in the mammals. 
6. Nerve foramina of ethmoid region 
Lastly, a brief account of those openings which serve for the 
entrance or exit of nerves. Of these nerves there are but two 
which need occupy our attention—the olfactory (together with 
the olfactory lobe) and the first, or ophthalmic, ramus of the 
trigeminal—renamed the ramus ethmoidalis on entrance to the 
nasal capsule. 
The olfactory fenestra (fig. 1, fen.ol.), divided into right and 
left halves by the septum nasale, is an enormous kite-shaped 
opening with rounded corners and lies in an almost horizontal 
plane. The lateral angles, formed by the union of the spheneth- 
moid cartilages with the tectum nasi, are approximately right 
angles; the anterior angle, formed by the posterior margin of 
the tectum, is obtuse, or, rather, is reduced to an almost semi- 
circular curve; the posterior angle, formed by the convergence 
and union of the sphenethmoid cartilages in the solum supra- 
septale, is decidedly acute. In the posterior part of the opening 
lie the long olfactory lobes, from which a very large number of 
nerve bundles extend into the nasal capsule (fig. 25, n.J. and 
n.I’.). Only a few of the bundles are indicated by the letters, 
the others are easily recognized. One pair of these bundles 
(n.[.) are marked out by their very large size and their more 
