CHONDROCRANIUM OF EUMECES 193 
lacking in Chelonia and Chelydra (Nick, ’12) and Emys (Kunkel, 
12 b). It is also absent in Vipera (Peyer, 712) and Crocodilus 
(Gaupp, 705 b; Shiino, 14). 
The paries nasi has been described above as ending posteriorly 
in a free margin; this is only partially true. From the pars 
triangularis this margin curves upward and backward and 
toward the median plane; thus the lateral wall, rapidly narrow- 
ing, is transformed into a posterior wall of the nasal capsule, the 
planum antorbitale (figs. 1, 2, and 3, pl.ant.). The narrowing 
of the wall occurs mainly at the lower edge, so that the free 
upper edge of the planum antorbitale lies just under the sphen- 
ethmoid cartilage and only very slightly below the upper edge 
of the nasal septum (fig. 3). The planum antorbitale is a nearly 
vertical plate, and extends almost transversely, although its 
inner end is very slightly posterior to the outer. In the neigh- 
borhood of the nasal septum its median end bends suddenly 
downward, then as suddenly forward, and goes over into the 
paraseptal cartilage (fig. 2, c.par.), to be described more fully 
in connection with the floor of the ethmoid region. It should 
be noted that the planum antorbitale remains entirely free from 
the septum, as in most reptiles—Sphenodon (Schauinsland, ‘U0), 
Chrysemys (Gaupp, ’05b), Emys (Gaupp, 705b; Kunkel, 
"12 b), Chelydra, Chelone, and Dermochelys (Nick, 712). In 
Dermochelys and Chelonia there is contact, but no fusion of the 
cartilages. Only in Crocodilus is a fusion reported, and here 
the data are contradictory. Gaupp (05 b) reports the planum 
antorbitale as free, while Shiino (14) describes it as uniting 
solidly with the septum. In Vipera (Peyer, 712) the entire 
planum antorbitale is lacking. In the Mammalia the planum 
antorbitale may be either free or attached, the latter condition 
being held as secondary by Gaupp, who stresses the freedom of 
the planum antorbitale in their reptilian ancestors as affording 
the opportunity for a shifting of the position of the posterior 
limit of the nasal capsule in the Mammalia— 
Die Nasenkapsel der Siuger leitet sich von einer Kapselform ab, 
bei der, wie z.B. bei Rhynchocephalen und Sauriern, die Hinterwand 
(d.i. die beiderseitigen Plana antorbitalia) sowie die Cartilago para- 
