45] THE NASAL ORGAN IN AMPHIBIA—HIGGINS 45 
related, both having retained these ancestral characters. An older larva 
of Spelerpes, also figured by Wiedersheim (Fig. 108), has a caudal extension 
of the antorbital process, which he calls the maxillary cartilage, whose 
relation to the pterygoid suggests an earlier relation between the two. 
In several of the Urodeles, as shown by figures of Parker (1876), and 
Wiedersheim (1877), a strong pterygoid reaches well forward from the 
quadrate, absent in some of my larvae but present in the adult. In the 
earlier larva of Amphiuma, a pterygoid process has not developed; but in 
the later stage it has chondrified well forward, nearly to the base of the 
antorbital. In all Urodeles, both processus antorbitalis and pterygoid are 
developed, but the proximity of the two varies greatly throughout the 
order, and I would hesitate to base any statement of relationships upon 
the relative extent of development of these structures; but no where except 
in Cryptobranchus and Ranodon is there any connection between them. 
The openness of the nasal capsule of Amphiuma, together with the 
somewhat specialized anterior part, renders it difficult of homology with the 
more typical Urodele, and suggests that it is far removed from any other 
Amphibian. However, in the early method of chondrification, and in the 
development of some of the parts, Amphiuma appears to be more closely 
allied to Cryptobranchus. In both, the cristae trabeculorum are formed 
early, as well as the planum verticale, the latter arising from the median 
line of the basale and later becoming associated with the columna eth- 
moidalis. Further relationship is evidenced in the origin of the tectale as 
a lateral growth from the columna, giving rise in Amphiuma to the elongate 
lamina externa, along the lateral surface of the nasal sac. Meagre as 
these relationships may seem, Amphiuma appears to be nearer Crypto- 
branchus than any other Urodele, the anterior parts of its capsule having 
become secondarily acquired. 
Although Salamandra resembles Amblystoma in some ways, the many 
differences between their capsules, such as the size of the planum verticale, 
the persistence of the foramen ethmoidalis in the former, and the origin of 
the ethmoidal columns, justifies their separation. In the persistence of 
the caudal process of the planum basale in the 25 mm. Salamandra, there 
is a resemblance to Cryptobranchus; but in the origin of the columnae 
ethmoidales from the medial margins of the cornua, Salamandra is more 
like Spelerpes. 
Triton and Diemictylus are far removed from the group just described, 
but are probably related to it through Salamandra. The complete 
development of a lamina medialis, with the deep internasal space, and the 
anterior position of the olfactory sac in respect to the forebrain, as well as 
the persistence throughout life of the fenestra ethmoidalis, are characters 
common to both Triton and Diemictylus. The complete loss of a pons 
ethmoidalis in Diemictylus converts the fenestra into a gap, only a mem- 
