736 B. W. KUNKEL 



margin of the septum, which Parker ('80) termed the 'prenasal 

 cartilage,' farther posteriorly the capsules extend much farther 

 ventrally so that there is a fairly deep median groove between the 

 two bulging capsules. The solum nasi projects posteriorly as 

 the cartilago ectochoanahs. Throughout the greater part of its 

 length the solum nasi is continuous with the septum, the foramen 

 praepalatinum and the slit separating the cartilago paraseptalis 

 and septum being the only points at which the floor is incomplete. 



The septum interorbitale continues into the septum nasi inter- 

 rupted only by a small cu'cular perforation situated near the 

 dorsal margin immediately in front of and between the bases of the 

 commissurae spheno-ethmoidales, so that there is formed a very 

 high ventral commissure and a slender, rodlike one between the 

 septum interorbitale and septum nasi. 



The septum nasi is a thin vertical plate with a longitudinal 

 ridge on each side, the crista longitudinaUs septi, wliich extends 

 from in front at the level of the upper margin of the fenestra 

 narina posteriorly and ventrally to the point at which the car- 

 tilago paraseptalis becomes separate from the septum (figs. 13 

 and 18). The septum is much shorter along its dorsal than along 

 its ventral margin, and is continuous anteriorly with the tectum 

 nasi, but posteriori}", in the region of the fenestra olfactoria, it 

 ends freely dorsally. The upper margin slopes downward in 

 front. The ventral margin is continuous with the floor of the 

 capsule except in the region of the foramen praepalatinum and 

 that of the short cartilago paraseptaUs. Like the upper margin it 

 slopes downward in front, but more rapidly than the upper mar- 

 gin so that the septum nasi is much higher in front than behind. 

 Especially in the region of the anterior half of the foramen prae- 

 palatinum the septum projects below the level of the floor of the 

 capsule to form a shght ventral crest along the mid-ventral line, 

 the prenasal cartilage of Parker. The front margin of the septum 

 is continuous in its dorsal half with the transverse vertical front 

 wall of the capsule and rounds off gradually into the dorsal mar- 

 gin; in its ventral half the septum ends freely between the two 

 fenestrae narinae to separate them completely from each other. 

 In a somewhat older stage of Emys than that modelled, Seydel 



