402 HARRIS HAWTHORNE WILDER ON 
all of the vertebrae, but is restricted to a certain region, approximately that of vertebra 
8 to 18. 
It would seem important to investigate the development of transverse process and 
rib in certain of the other vertebrae, for example the 2d and the 4th. Regarding the 
sacral vertebra and its rib, as stated previously, Géppert’s conclusion, which does not 
allow a complete homology with the rest of the vertebral column, seems anatomically 
improbable. 
Tur SKULL AND VISCERAL SKELETON. 
Anatomically, the bones of the head consist of (1) the skull in the restricted sense, 
which includes the cranium, the ear capsules, and the upper jaw pieces, (2) the nasal and 
optic capsules, and (3) the visceral skeleton, represented by the mandible, the hyobran- 
chial apparatus, and the laryngeal cartilages. In point of origin the elements are three 
in number: (1) the primitive cartilage, still seen in the sense capsules, the primordial 
cranium, and the most of the visceral skeleton; (2) cartilage bones, or ossifications of 
localized portions of the primary cartilage; and (3) dermal bones of integmental origin, 
investing the surface of the cartilage in skull and mandible. 
Although there are osseous elements from two sources, the proportion of unossified 
cartilage left in the adult head is very great and compares in this respect with the condi- 
tion seen in the Chondrostei rather than with that of other fishes or of most amphibians. 
This large amount of cartilage is very suggestive of an embryonic or immature form, and 
suggests either the possibility which has already been frequently expressed, that Necturus 
is in a sense a permanent larva, as is the case with the Axolotl, or that it is an exceed- 
ingly primitive form, perhaps nearer the fishes than any other amphibian. 
An orderly treatment of this complex bit of anatomy is extremely difficult and may 
perhaps be facilitated by the presentation of a classification of the subject, which will be 
adhered to in the later description. 
GENERAL DeEscrIPTION. 
Tur CHONDROCRANIUM. 
Tut Ossrous ELEMENTS. 
(a.) Otie and occipital regions. 
1. Pro-otie. 
2. Opisthotic. 
3. Exoccipital. 
4. Quadratum. 
5 and 6, Paraquadratum and operculum. 
