NECTURUS MACULATUS. 405 
The chondrocranium consists essentially of a delicate framework which runs around 
the entire cranial cavity and with which certain other cartilaginous elements are associ- 
ated in varying degrees of intimacy of relation. The framework consists in the embryo 
of a pair of lateral bars, placed parallel to one another and divisible into an anterior ele- 
ment, the trabecula, and a posterior, or parachordal element. In the adult these names 
are retained as designations for the regions corresponding to those elements, the trabecu- 
lar region being that anterior to the otic capsules, while the part associated directly with 
' the capsules themselves is the parachordal region. Posteriorly, between the otic capsules 
the frame is completed by a pair of cartilaginous bands or arches, of which one, the supra- 
occipital arch,’ passes dorsal to the nerve cord, and the other, the basi-occipital arch, lies 
ventral to this latter part. According to Miss Platt, the supra-occipital arch is really the 
neural arch of a vertebra anterior to the atlas, which has fused with the skull to increase 
its strength. At the anterior end of the skull the frame is completed by the development 
of an internasal plate which connects the convergent trabeculae. Anterior to this the 
free ends of the trabeculae are continued a short distance in the form of small rostral 
processes. 
Of the originally external elements, the two large otic capsules are the most 
intimately related and are completely fused with the posterior portion of the primary part 
and thus form the largest and most voluminous portion of the chondrocranium. Anterior 
to these are the semi-detached quadrate cartilages, connected with the sides of the tra- 
becular frame by a narrow process, the trabeculo-quadrate isthmus. Still farther forward 
and separated from the latter by an interval in which are situated the eye and its acces- 
sory organs, appears a pair of distinct cartilages, attached to the trabeculae by connective 
tissue. These are the ante-orbital processes plainly representing a rudiment of the sub- 
ocular arch, or pterygo-quadrate process, so enormously developed in the frog and other 
Anura, an homology suggested by W. K. Parker’s term of “ ethmo-palatine process.” 
The other cartilaginous parts topographically associated with the chondrocranium are 
the nasal and optic capsules, of which the former lies directly upon the anterior end of 
the completed skull, and barely comes in contact with the chondrocranium, while the 
latter is completely isolated. These parts will receive separate treatment later. 
The ossifications of the chondrocranium (= “cartilage bones”) are few in number in 
comparison with those of most Urodeles and consist of but four pairs: (1) the quadrates, 
used to form a strong support for the mandible, (2) the exoccipitals, forming the condyles 
1Miss Platt objects to the term “‘occipitale superius” for the dorsal cartilaginous arch on the ground that the supra- 
occipital is not an amphibian bone and prefers “interoccipitale,” as suggested to her by Gaupp. This term, however, leaves 
out of account the ventral arch, unless we use the terms “interoccipitale dorsale ” and ‘ interoccipitale ventrale ” which are 
cumbersome and possess the disadvantage of the substitution of new terms for old and readily understood ones. Moreover, 
a portion of the Amniote supra-occipital is preformed in cartilage,and it seems more than probable that there is at least a 
partial homology between it and the cartilaginous arch found here. The same may also be said of the basi-occipital piece. 
