32 ILLINOIS BIOLOGICAL MONOGRAPHS [32 



In an older larva, a more complete nasal capsule (Fig. 30) has been 

 formed, which resembles in but few respects those of other Urodeles. It is 

 somewhat ovoid in outline, its greatest width being about one-fifth its 

 length. From the anterior end of the crista, each trabecula, relatively 

 more slender than before, inclines medially and passing along the lower 

 margin of the olfactory lobe, unites with its fellow at about the level of the 

 middle of the capsule, to form the planum basale (pb). This plate is 

 considerably larger than before, and together with the cornu of either 

 side, forms a plate rtfughly hexagonal in outline. Its posterior margin is 

 straight, while lateral to the line of the trabecula, its caudal margin is 

 directed antero-laterally to a point corresponding to the lateral angle of the 

 cornu of the early stage, where it fuses with another cartilage bar yet to be 

 described. Each lateral-cephalic margin is also curved and is produced 

 in front, in a line with the trabecula, into a process directed forward from 

 the planum, the anterior extension of the trabecula. These cornual tips 

 are separated by an internasal space somewhat wider although much 

 shorter than before. 



The planum verticale (pv) arises from the anterior half of the basale, 

 just back of the internasal space, as a narrow band of cartilage, which 

 separates the nasal organs in this region (Fig. 69, pv). Dorsally the planum 

 verticale divides into two bars, the alary processes, which are inclined to 

 each other at about an angle of 60 degrees. Each alary process is con- 

 tinuous with the columna ethmoidalis, and partially covers the antero- 

 median surface of the olfactory sac. 



The columna ethmoidalis is now complete, extending forward from the 

 crista to, and slightly beyond, the alary process. Apparently this cor- 

 responds to the bar arising from the superior margin of the crista of the 

 earlier stage, as far as and including the small process dorsal to the nasal 

 sac described above. The more lateral portion of the earlier bar is evi- 

 dently the lamina externa of this stage, which now extends forwards along 

 the lateral surface of the nasal organ. At about the level of the planum 

 verticale, the lamina externa (le) sends a process downwards, which unites 

 with the lateral angle of the cornu. The lamina externa continues beyond 

 this junction as a broader plate, ending in an oblique circumnarial carti- 

 lage ring surrounding the narial aperture. 



The antorbital process is much as before, being inclined at an angle of 

 about 30 degrees from the trabecula, rather than at right angles to it as in 

 most other Urodeles. 



Many of the characters of the nasal capsule of the adult Amphiuma, 

 as described by Wilder (1892), appear in a larva 82 mm. long. The nasal 

 capsule (Fig. 31) has doubled in size, although the proportions are un- 

 changed; additional chondrification having occurred in the anterior parts. 

 The crista trabeculae, antorbital process, trabecula, planum basale, and 



