PAPERS ON BIOLOGY AND AGRICULTURE 125 



In the older stage, that of 75mm. total length, chondri- 

 fication is more advanced. The nasal capsule of this 

 stage consists of two curving plates of cartilages con- 

 nected in the median line, forming the body of the cap- 

 sule as in the earlier stage. 



The trabecular, which form the floor of the chondro- 

 cranium in the region of the brain as before, unite an- 

 teriorly to form the septum nasi, now considerably 

 broader and longer than in the earlier stage (Fig. 8). 

 The comu trabeculae, which are the anterior expansions 

 of the septum nasi, are more elongate and extend ven- 

 trally and somewhat posteriorly, ending in a process ven- 

 tral but still in a plane with the external naris (Fig. 7). 

 The part of the nasal capsule which covers the anterior 

 portion of the nasal organ is now more curved in appear- 

 ance. The tectum nasale reaches more posteriorly, and 

 bending ventrally covers a considerable portion of the 

 nasal organ (Figs. 8, 10). Anteriorly, it is continuous 

 with the cupola, as in the younger stage, which forms 

 the anterior covering of the nasal organ, and forms part 

 of the wall of the capsule in this region (Fig. 9). The 

 prominent process formed by the ventral extension of 

 the cupola lateral to the narial opening curves posteri- 

 orly, and although ending bluntly here, would in all 

 probability unite with the small lateral process of the 

 tectum nasale to form a complete oval narial fenestra 

 (Fig. 9). Such a fusion has already occurred in the older 

 lizard embryo described by Gaupp, and no doubt is true 

 here as well. 



The planum lateralis, which forms the lateral wall of 

 the posterior part of the capsule, becomes more expanded 

 than before, and bending in a median ventral direction, 

 ends in a knob-like process which makes a conspicuous 

 U-shaped bend closely applied to, but not connected with 

 the septum nasi (Figs. 8, 9). This new plate covering 

 the posterior parts of the nasal organ now forms the 

 posterior wall of the nasal capsule, and following the 

 terminology of authors may well be called the planum 

 antorbitale. The lateral and ventral margin of this 

 curved planum antorbitale is conspicuous by three dee]) 

 indentations, thus giving it a marked serrate appear- 



