21) THE NASAL ORGAN IN AMPHIBIA—HIGGINS 21 
Amblystoma is called the infra-conchalis, separated from the naris by a 
cartilage bar; while the posterior part of Jacobson’s organ rests upon a 
shelf formed by the prolongation of the cornu. The orbito-nasal foramen, 
the choanal opening, and the relation of the olfactory organ to the capsule, 
are features common to both Amblystoma and Diemictylus; and yet the 
absence of a planum verticale, the greatly reduced planum basale and the 
complete continuity of internasal space with cavum cranii in the latter 
form, preclude the determination of close relationships here. 
CRYPTOBRANCHUS ALLEGHANIENSIS 
Practically no work has been done upon the development of the skeleton 
in the larval stages of Cryptobranchus, although the adult skull and nasal 
structures have been described by Parker (1876), Wiedersheim (1877), and 
Wilder (1892). I have studied four stages in the chondrification of the 
nasal capsule, and although my material lacks some intermediate steps in 
the process, yet I am able to recognize the method of development and to 
note some features that may prove interesting from a phylogenetic point 
of view. 
The early process of chondrification in Cryptobranchus is similar to 
that in Amblystoma, and my earliest stage suggests the eleven mm. larva 
of that animal with certain additional features. In a larval Cryptobran- 
chus two weeks after hatching (Fig. 22), a nasal capsule has not yet formed. 
The cristae trabeculorum (cr ¢) are very strong and high, but terminate 
abruptly near the anterior margin of the eye; while the trabeculae continue 
anteriorly, turning slightly medially but not meeting to form the planum 
basale. Each is curved upon its medial surface, which rests against the 
olfactory lobe; while anteriorly a ventral lateral expansion of the trabecula 
is the beginning of the cornu (ct), which resembles Amblystoma, and ends 
in a blunt process in the surrounding tissue. 
In contrast to the eleven mm. Amblystomal larva, trabecular crests 
are well developed in this stage of Cryptobranchus; while on the other 
hand, the cornua trabeculorum which are well developed in the young 
Amblystoma are just beginning to chondrify in Cryptobranchus. Antor- 
bital processes have not formed, nor is there any trace of an ethmoidal 
column as in the youngest Amblystoma. 
In a larva five weeks after hatching (Fig. 23), chondrification has ad- 
vanced in all parts, but the absence of an intermediate stage prevents a 
definite conclusion as to the origin of certain structures. In general the 
capsule resembles in many respects that of the 25 mm. Salamandra. 
From the anterior end of the crista, each trabecula inclines toward the 
median line for a short distance, and then passes straight forward and is 
united with its mate by a small planum basale (6) similar in size to that in 
Triton cristatus. This planum basale differs from that of any Urodele thus 
