23] THE NASAL ORGAN IN AMPHIBIA— HIGGINS 23 



in the earlier stage. A wide bay, the fenestra narina, marks the anterior 

 boundary of the tectale, and here, as in Amblystoma, is a larval character, 

 disappearing in the adult. The cornu trabeculae is somewhat wider than 

 before, although differing considerably from the Ijroader cornua of other 

 Urodeles, A small notch at the anterior end of the cornu conducts a 

 second branch of the nasalis internus from the capsule. 



In the last stage of Cryptobranchus studied, a larva three months old 

 (Fig. 24), chondrification has advanced in all parts, forming a well-defined 

 nasal capsule, resembling in some respects the 45 mm. Amblystoma. The 

 planum basale and verticale are much as before, supporting the olfactory 

 lobes, and uniting the capsules of the two sides just anterior to the olfactory 

 foramina. Anterior to the planum verticale, the lamina medialis {Itn) 

 formed by both ethmoidal column and trabecula, together with the cornu 

 forms the anterior cupola of the capsule, which is pierced by two foramina, 

 one medial and the other ventral, through which the branches of the 

 nasalis internus nerve leave the capsule. The olfactory duct continues 

 forward beyond the lateral margin of the cupola and opens through the 

 external naris, anterior to all capsular structures. 



The cornu trabeculae is much as in the earlier stage, except that it has 

 now united to the anterior extension of the planum tectale, just as in all 

 other Urodeles thus far described; and the organ of Jacobson rests upon the 

 caudal extension of the cornu behind this connection. The tectale itself 

 is larger than before, reaching forward a short distance beyond its junction 

 with the cornu, thus completely covering the choana and the dorsal parts 

 of the nasal sac. The fenestra narina is deeper than before, extending 

 back from the naris to the planum verticale. A branch of the superficialis 

 nerve enters and leaves the capsule through this bay; but in a later stage, 

 cartilage has chondrified around these nerves leaving two small foramina, 

 and completely obliterating the narina, as in the last larval stage of 

 Amblystoma. 



In this stage, the bar of cartilage mentioned in connection wth the five 

 weeks larva as extending at right angles from the side of the trabecula, has 

 attained such relations as to throw light upon its morphology. At its tip 

 it is directly connected with the anterior end of the pterygoquadrate bar, 

 which extends back to the otic region where the relations are much the same 

 as in all Urodeles. This completeness of connection of the pterygoquad- 

 rate with the anterior parts of the trabecula is paralleled, so far as I know, 

 only in the Siberian genus Ranodon (Wiedersheim 1877, Fig. 69), and is 

 lost in the adult of Cryptobranchus, both our species and the Japanese 

 japonicus. 



Some years ago, Gaupp questioned a statement by Kingsley (1892, 

 p. 672), who said: "the lower process may retain the name 'antorbital', 

 usually applied to it, for Amphiuma presents no evidence that it is the 



