33] THE NASAL ORGAN IN AMPHIBIA— HIGGINS 33 



columna ethmoidalis are much as in the younger stage, and need no further 

 description. The dorsal surface of the capsule, however, has been changed 

 by the continuation forward of the ethmoidal column to a junction with 

 the circumnarial cartilage and a lateral extension of the cartilage from the 

 column to the lamina externa; so that the whole anterior end of the capsule 

 is roofed in as far back as the level of the verticale, this roof being perfor- 

 ated behind and near its median line for the passage of the nasalis internus 

 of the profundus. The lamina externa, behind its connection with the 

 cornu is wider than before, and close to the lower margin near its anterior 

 end is a smaller foramen for the nasalis externus of the profundus, where 

 it passes to the external nasal glands. 



The chondrification of the anterior parts of the capsule has outlined a 

 large gap upon the dorsal surface, bounded by the columna ethmoidalis, 

 lamina externa and anterior tectale, resembling in shape the large dorsal 

 gap in Amblystoma. The floor of the capsule is represented by the cornu 

 trabeculae and the antorbital process; the latter has not united to any 

 more anterior capsular part, so that a foramen orbito-nasalis does not 

 exist, nor does Wilder describe one in the adult. 



The nasal capsule of Amphiuma differs considerably from that of any 

 urodele thus far described. The large vacuities in the dorsal, lateral and 

 ventral surfaces and the consequent lack of skeletal protection of the nasal 

 epithelium is much in contrast to either Salamandra or Amblystoma and 

 may represent either a reduction in parts or a permanent larval condition. 

 So far as I know, a circumnarial ring does not exist in any other Urodele, 

 the anterior part of the capsule being vaulted in all others, with the excep- 

 tion of the Caecilians and Necturus. The fusion of the planum basale with 

 the cornua trabeculorum to form the hexagonal plate, is not common for 

 other capsules, where in the older stages these parts are considerably 

 removed from each other. 



The narrow planum verticale develops dorsally from the median line of 

 the planum basale, somewhat as in Cryptobranchus, and then unites 

 laterally to the ethmoidal column which, as in Spelerpes, probably devel- 

 oped anteriorly from the cephalic margin of the trabecular crest. In no 

 other capsule, thus far described, with the exception of Necturus, is there a 

 complete absence of the lamina medialis. Anterior to the verticale the 

 nasal organs are separated by membrane only, a wide gap extending from 

 the medial margin of the cornu to the anterior tectale. 



Amphiuma appears to be far removed from other Urodeles. It cannot 

 be regarded as ancestral, as it is difficult to homologize the capsule of this 

 animal, even in the early larval stages, with that of other genera; but it 

 probably is reduced from more typical conditions more closely related to 

 either Spelerpes or Cryptobranchus. In the origin of the verticale and in the 

 form of the cornu which unites to the anterior extension of the externa. 



