DEVELOPMENT OF THE SKULL OF EMYS 759 



men praepalatinum is not closed posteriorly by a fusion of the 

 cartilago paraseptalis with the septum, but extends freely pos- 

 teriorly for a considerable distance. 



33. The septum nasi in the stage modelled is continuous with 

 the solum nasi except in the region of the foramen praepalatinum. 



34. The cartilago paraseptalis, limiting the fenestra basalis 

 medially, does not fuse with the planum antorbitale dorsally so 

 that in the stage modelled the fenestra basalis is not completely 

 enclosed with cartilage. 



35. A rudimentary concha is present in the form of a shallow 

 longitudinal infolding of the paries nasi. In older stages this 

 is increased in height by a thickening of the wall which projects 

 in a medial direction. 



36. The septum nasi is thickened by means of a longitudinal 

 crest, the crista longitudinalis septi, which separates the pars 

 respiratoria from the pars olfactoria of the olfactory sac. 



37. A slender rod, the pila supraglandularis, attached poste- 

 riorly to the septum in the region of the foramen praepalatinum, 

 extends forward parallel to the crista longitudinalis septi above 

 the glandula nasalis media and ends freely in front a short dis- 

 tance behind the level of the fenestra narina. 



38. The septum nasi is provided with a small fenestra very 

 near its dorsal margin in the region of the fenestra olfactoria. 



39. The prenasal cartilage is present as a median ridge on the 

 ventral side of the anterior part of the capsule. 



40. A small foramen epiphaniale is present. 



41. The palatoquadratum is entirely separate from the cra- 

 nium and exhibits a distinct processus pterygoideus which in turn 

 supports a processus ascendens which is the homologue of the 

 'columella' of the Lacertilia. 



42. The pars quadrata of the palatoquadratum may be differ- 

 entiated into a large hollow pars mastoidea, enclosing an exten- 

 sion of the tympanic cavity, and the pars articularis. 



43. The posterior margin of the quadratum is deeply incised 

 by the incisura columellae for the accommodation of the columella 

 auris. 



