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, 
