DEVELOPMENT OF THE SKULL OF EMYS 731 



the cartilage paraseptalis ventrally, and the planum antorbitale 

 forming the postero-dorsal wall wliich separates the olfactory 

 sac from the orbit. These regions for the most part pass over 

 into each other by even transitions. 



The entire dorsal and posterior portion of the capsule, as 

 Seydel has already shown, is free from the septmn as is also the 

 case in Lacerta; that is, the planum antorbitale terminates freely 

 above and behind. Besides the connection between the septum 

 nasi and the walls of the capsule there is a further connection of 

 the capsule with the rest of the skull by means of the commissura 

 spheno-ethmoidalis, a cartilaginous rod extending posteriorly from 

 the tectum nasi on each side to the anterior extremity of the 

 planum supraseptale, where the latter passes into the septum 

 supraseptale, and enclosing the two fenestrae olfactoriae on the 

 sides, and thus separating the fenestra olfactoria from the fissura 

 orbitonasalis. 



The capsule opens in front to accommodate the apertura nasalis 

 externa, by the fenestra narina, and posteriorly by the fenestrae 

 basales for the choanae. There is a longitudinal slit in the floor 

 of the capsule which Seydel has called the foramen praepalatinum. 

 The capsule is perforated dorsally by the fenestrae olfactoriae, 

 ventral to which on each side is the fissura orbitonasaUs, through 

 the most dorsal part of which the ethmoidal branch of the ramus 

 ophthalmicus n. trigemini passes in its course from the orbit to 

 the olfactory sac. Besides these openings there is also a small 

 foramen epiphaniale for the passage of the n. lateraUs nasi rami 

 ophthalmic! from the capsule to the exterior. A foramen apicale 

 is lacking in all stages studied. 



In contrast to Lacerta the entire capsule is shifted ventrally 

 and so rotated that the anterior end is shghtly ventral to the 

 posterior end. This change in position is indicated partly by the 

 fact that the plane of the fenestra olfactoria is inclined from the 

 horizontal, as in Lacerta, so that its ventral end is below the pos- 

 terior. Besides this, the capsule is somewhat compressed later- 

 ally so that its floor is pressed ventrally and extends well below 

 the lower margin of the septum nasi. The two halves of the cap- 

 sule are thus separated on the under side by a groove which 



